Cellularsenescence is reportedly involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). We previously showed that 27-hydroxycholesterol (27-OHC) is elevated in the airways of COPD patients compared with those in healthy subjects. The aim of this study was to investigate whether lung fibroblasts of COPD patients are senescent and to determine the effects of 27-OHC on senescence of lung resident cells, including fibroblasts and airway epithelial cells. Localization of senescence-associated proteins and sterol 27-hydroxylase was investigated in the lungs of COPD patients by immunohistochemical staining. To evaluate whether 27-OHC acceleratescellularsenescence, lung resident cells were exposed to 27-OHC. Senescence markers and fibroblast-mediated tissue repair were investigated in the 27-OHC-treated cells. Expression of senescence-associated proteins was significantly enhanced in lung fibroblasts of COPD patients. Similarly, expression of sterol 27-hydroxylase was significantly upregulated in lung fibroblasts and alveolar macrophages in these patients. Treatment with the concentration of 27-OHC detected in COPD airways significantly augmented expression of senescence-associated proteins and senescence-associated β-galactosidase activity, and delayed cell growth through the prostaglandin E2-reactive nitrogen species pathway. The 27-OHC-treated fibroblasts impaired tissue repair function. Fibroblasts from lungs of COPD patients showed acceleratedsenescence and were more susceptible to 27-OHC-induced cellularsenescence compared with those of healthy subjects. In conclusion, 27-OHC acceleratescellularsenescence in lung resident cells and may play a pivotal role in cellularsenescence in COPD. PMID:27036870

Magnesium inadequacy affects more than half of the U.S. population and is associated with increased risk for many age-related diseases, yet the underlying mechanisms are unknown. Altered cellular physiology has been demonstrated after acute exposure to severe magnesium deficiency, but few reports have addressed the consequences of long-term exposure to moderate magnesium deficiency in human cells. Therefore, IMR-90 human fibroblasts were continuously cultured in magnesium-deficient conditions to determine the long-term effects on the cells. These fibroblasts did not demonstrate differences in cellular viability or plating efficiency but did exhibit a decreased replicative lifespan in populations cultured in magnesium-deficient compared with standard media conditions, both at ambient (20% O(2)) and physiological (5% O(2)) oxygen tension. The growth rates for immortalized IMR-90 fibroblasts were not affected under the same conditions. IMR-90 fibroblast populations cultured in magnesium-deficient conditions had increased senescence-associated beta-galactosidase activity and increased p16(INK4a) and p21(WAF1) protein expression compared with cultures from standard media conditions. Telomere attrition was also accelerated in cell populations from magnesium-deficient cultures. Thus, the long-term consequence of inadequate magnesium availability in human fibroblast cultures was acceleratedcellularsenescence, which may be a mechanism through which chronic magnesium inadequacy could promote or exacerbate age-related disease. PMID:18391207

The p53 tumor suppressor plays a key role in organismal aging. A cellular mechanism postulated to drive the aging process is cellularsenescence, mediated in part by p53. Although senescent cells accumulate in elderly individuals, most studies have relied on correlating in vitro senescence assays with in vivo phenotypes of aging. Here, using two different mouse models in which the p53-related protein p63 is compromised, we demonstrate that cellularsenescence and organismal aging are intimately linked and that these processes are mediated by p63 loss. We found that p63+/- mice have a shortened life span and display features of accelerated aging. Both germline and somatically induced p63 deficiency activates widespread cellularsenescence with enhanced expression of senescent markers SA-β-gal, PML, and p16INK4a. Using an inducible tissue-specific p63 conditional model, we further show that p63 deficiency induces cellularsenescence and causes accelerated aging phenotypes in the adult. Our results thus suggest a causative link between cellularsenescence and aging in vivo, and demonstrate that p63 deficiency accelerates this process. PMID:16107615

Methamphetamine is a highly addictive psychostimulant that causes profound damage to the brain and other body organs. Post mortem studies of human tissues have linked the use of this drug to diseases associated with aging, such as coronary atherosclerosis and pulmonary fibrosis, but the molecular mechanism underlying these findings remains unknown. Here we used functional lipidomics and transcriptomics experiments to study abnormalities in lipid metabolism in select regions of the brain and, to a greater extent, peripheral organs and tissues of rats that self-administered methamphetamine. Experiments in various cellular models (primary mouse fibroblasts and myotubes) allowed us to investigate the molecular mechanisms of systemic inflammation and cellular aging related to methamphetamine abuse. We report now that methamphetamine acceleratescellularsenescence and activates transcription of genes involved in cell-cycle control and inflammation by stimulating production of the sphingolipid messenger ceramide. This pathogenic cascade is triggered by reactive oxygen species, likely generated through methamphetamine metabolism via cytochrome P450, and involves the recruitment of nuclear factor-κB (NF-κB) to induce expression of enzymes in the de novo pathway of ceramide biosynthesis. Inhibitors of NF-κB signaling and ceramide formation prevent methamphetamine-induced senescence and systemic inflammation in rats self-administering the drug, attenuating their health deterioration. The results suggest new therapeutic strategies to reduce the adverse consequences of methamphetamine abuse and improve effectiveness of abstinence treatments. PMID:25671639

Current evidence implicates intervertebral disc degeneration as a major cause of low back pain, although its pathogenesis is poorly understood. Numerous characteristic features of disc degeneration mimic those seen during ageing but appear to occur at an accelerated rate. We hypothesised that this is due to acceleratedcellularsenescence, which causes fundamental changes in the ability of disc cells to maintain the intervertebral disc (IVD) matrix, thus leading to IVD degeneration. Cells isolated from non-degenerate and degenerate human tissue were assessed for mean telomere length, senescence-associated β-galactosidase (SA-β-gal), and replicative potential. Expression of P16INK4A (increased in cellularsenescence) was also investigated in IVD tissue by means of immunohistochemistry. RNA from tissue and cultured cells was used for real-time polymerase chain reaction analysis for matrix metalloproteinase-13, ADAMTS 5 (a disintegrin and metalloprotease with thrombospondin motifs 5), and P16INK4A. Mean telomere length decreased with age in cells from non-degenerate tissue and also decreased with progressive stages of degeneration. In non-degenerate discs, there was an age-related increase in cellular expression of P16INK4A. Cells from degenerate discs (even from young patients) exhibited increased expression of P16INK4A, increased SA-β-gal staining, and a decrease in replicative potential. Importantly, there was a positive correlation between P16INK4A and matrix-degrading enzyme gene expression. Our findings indicate that disc cell senescence occurs in vivo and is accelerated in IVD degeneration. Furthermore, the senescent phenotype is associated with increased catabolism, implicating cellularsenescence in the pathogenesis of IVD degeneration. PMID:17498290

Current evidence implicates intervertebral disc degeneration as a major cause of low back pain, although its pathogenesis is poorly understood. Numerous characteristic features of disc degeneration mimic those seen during ageing but appear to occur at an accelerated rate. We hypothesised that this is due to acceleratedcellularsenescence, which causes fundamental changes in the ability of disc cells to maintain the intervertebral disc (IVD) matrix, thus leading to IVD degeneration. Cells isolated from non-degenerate and degenerate human tissue were assessed for mean telomere length, senescence-associated beta-galactosidase (SA-beta-gal), and replicative potential. Expression of P16INK4A (increased in cellularsenescence) was also investigated in IVD tissue by means of immunohistochemistry. RNA from tissue and cultured cells was used for real-time polymerase chain reaction analysis for matrix metalloproteinase-13, ADAMTS 5 (a disintegrin and metalloprotease with thrombospondin motifs 5), and P16INK4A. Mean telomere length decreased with age in cells from non-degenerate tissue and also decreased with progressive stages of degeneration. In non-degenerate discs, there was an age-related increase in cellular expression of P16INK4A. Cells from degenerate discs (even from young patients) exhibited increased expression of P16INK4A, increased SA-beta-gal staining, and a decrease in replicative potential. Importantly, there was a positive correlation between P16INK4A and matrix-degrading enzyme gene expression. Our findings indicate that disc cell senescence occurs in vivo and is accelerated in IVD degeneration. Furthermore, the senescent phenotype is associated with increased catabolism, implicating cellularsenescence in the pathogenesis of IVD degeneration. PMID:17498290

The aging of organisms is characterized by a gradual functional decline of all organ systems. Mammalian somatic cells in culture display a limited proliferative life span, at the end of which they undergo an irreversible cell cycle arrest known as replicative senescence. Whether cellularsenescence contributes to organismal aging has been controversial. We investigated telomere dysfunction, a recently discovered biomarker of cellularsenescence, and found that the number of senescent fibroblasts increases exponentially in the skin of aging baboons, reaching >15% of all cells in very old individuals. In addition, the same cells contain activated ataxia-telangiectasia mutated kinase and heterochromatinized nuclei, confirming their senescent status. PMID:16456035

For most species, aging promotes a host of degenerative pathologies that are characterized by debilitating losses of tissue or cellular function. However, especially among vertebrates, aging also promotes hyperplastic pathologies, the most deadly of which is cancer. In contrast to the loss of function that characterizes degenerating cells and tissues, malignant (cancerous) cells must acquire new (albeit aberrant) functions that allow them to develop into a lethal tumor. This review discusses the idea that, despite seemingly opposite characteristics, the degenerative and hyperplastic pathologies of aging are at least partly linked by a common biological phenomenon: a cellular stress response known as cellularsenescence. The senescence response is widely recognized as a potent tumor suppressive mechanism. However, recent evidence strengthens the idea that it also drives both degenerative and hyper-plastic pathologies, most likely by promoting chronic inflammation. Thus, the senescence response may be the result of antagonistically pleiotropic gene action. PMID:23140366

For most species, aging promotes a host of degenerative pathologies that are characterized by debilitating losses of tissue or cellular function. However, especially among vertebrates, aging also promotes hyperplastic pathologies, the most deadly of which is cancer. In contrast to the loss of function that characterizes degenerating cells and tissues, malignant (cancerous) cells must acquire new (albeit aberrant) functions that allow them to develop into a lethal tumor. This review discusses the idea that, despite seemingly opposite characteristics, the degenerative and hyperplastic pathologies of aging are at least partly linked by a common biological phenomenon: a cellular stress response known as cellularsenescence. The senescence response is widely recognized as a potent tumor suppressive mechanism. However, recent evidence strengthens the idea that it also drives both degenerative and hyperplastic pathologies, most likely by promoting chronic inflammation. Thus, the senescence response may be the result of antagonistically pleiotropic gene action. PMID:23140366

The cellularsenescence definition comes to the fact of cells irreversible proliferation disability. Besides the cell cycle arrest, senescent cells go through some morphological, biochemical, and functional changes which are the signs of cellularsenescence. The senescent cells (including replicative senescence and stress-induced premature senescence) of all the tissues look alike. They are metabolically active and possess the set of characteristics in vitro and in vivo, which are known as biomarkers of aging and cellularsenescence. Among biomarkers of cellularsenescence telomere shortening is a rather elegant frequently used biomarker. Validity of telomere shortening as a marker for cellularsenescence is based on theoretical and experimental data. PMID:26805432

The cellularsenescence definition comes to the fact of cells irreversible proliferation disability. Besides the cell cycle arrest, senescent cells go through some morphological, biochemical, and functional changes which are the signs of cellularsenescence. The senescent cells (including replicative senescence and stress-induced premature senescence) of all the tissues look alike. They are metabolically active and possess the set of characteristics in vitro and in vivo, which are known as biomarkers of aging and cellularsenescence. Among biomarkers of cellularsenescence telomere shortening is a rather elegant frequently used biomarker. Validity of telomere shortening as a marker for cellularsenescence is based on theoretical and experimental data. PMID:26805432

Autophagy and the ubiquitin–proteasome pathway (UPP) are the major protein degradation systems in eukaryotic cells. Whereas the former mediate a bulk nonspecific degradation, the UPP allows a rapid degradation of specific proteins. Both systems have been shown to play a role in tumorigenesis, and the interest in developing therapeutic agents inhibiting protein degradation is steadily growing. However, emerging data point to a critical role for autophagy in cellularsenescence, an established tumor suppressor mechanism. Recently, a selective protein degradation process mediated by the UPP was also shown to contribute to the senescence phenotype. This process is tightly regulated by E3 ubiquitin ligases, deubiquitinases, and several post-translational modifications of target proteins. Illustrating the complexity of UPP, more than 600 human genes have been shown to encode E3 ubiquitin ligases, a number which exceeds that of the protein kinases. Nevertheless, our knowledge of proteasome-dependent protein degradation as a regulated process in cellular contexts such as cancer and senescence remains very limited. Here we discuss the implications of protein degradation in senescence and attempt to relate this function to the protein degradation pattern observed in cancer cells. PMID:24866342

Aging is the largest risk factor for most chronic diseases, which account for the majority of morbidity and health care expenditures in developed nations. New findings suggest that aging is a modifiable risk factor, and it may be feasible to delay age-related diseases as a group by modulating fundamental aging mechanisms. One such mechanism is cellularsenescence, which can cause chronic inflammation through the senescence-associated secretory phenotype (SASP). We review the mechanisms that induce senescence and the SASP, their associations with chronic disease and frailty, therapeutic opportunities based on targeting senescent cells and the SASP, and potential paths to developing clinical interventions. PMID:23454759

Cellularsenescence is generally defined as an irreversible state of G1 cell cycle arrest in which cells are refractory to growth factor stimulation. Cellularsenescence can be induced through several different mechanisms. Primary mammalian cells display a finite life span, suggesting a mechanism that counts cell divisions. Those cells initially proliferate but eventually enter a state of permanent growth arrest, called replicative senescence. Erosion of telomeric DNA has emerged as a key factor in replicative senescence, which is antagonized during cell immortalization. Nevertheless, besides telomere shortening, there are other mechanisms inducing a growth arrest similar to the replicative senescencent phenotype. Oncogenic or mitogenic signals as well as DNA damage can induce such a phenotype of cellularsenescence. All forms of cellularsenescence share common signaling pathways and morphological features. Thereby, p53 seems to be essential for the senescence response. Many of these senescence inducing mechanisms can be experimentally recapitulated by the introduction of defined genetic elements. Replicative senescence due to telomere shortening can, for example, be induced by a dominant negative version of telomerase, premature senescence by the overexpression of oncogenic ras, or p16. PMID:17634581

Cellularsenescence has been widely recognized as a tumor suppressing mechanism that acts as a barrier to cancer development after oncogenic stimuli. A prominent in vivo model of the senescence barrier is represented by nevi, which are composed of melanocytes that, after an initial phase of proliferation induced by activated oncogenes (most commonly BRAF), are blocked in a state of cellularsenescence. Transformation to melanoma occurs when genes involved in controlling senescence are mutated or silenced and cells reacquire the capacity to proliferate. Pirin (PIR) is a highly conserved nuclear protein that likely functions as a transcriptional regulator whose expression levels are altered in different types of tumors. We analyzed the expression pattern of PIR in adult human tissues and found that it is expressed in melanocytes and has a complex pattern of regulation in nevi and melanoma: it is rarely detected in mature nevi, but is expressed at high levels in a subset of melanomas. Loss of function and overexpression experiments in normal and transformed melanocytic cells revealed that PIR is involved in the negative control of cellularsenescence and that its expression is necessary to overcome the senescence barrier. Our results suggest that PIR may have a relevant role in melanoma progression. PMID:21514450

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States, and cigarette smoking is the major risk factor for COPD. Fibroblasts play an important role in repair and lung homeostasis. Recent studies have demonstrated a reduced growth rate for lung fibroblasts in patients with COPD. In this study we examined the effect of cigarette smoke extract (CSE) on fibroblast proliferative capacity. We found that cigarette smoke stopped proliferation of lung fibroblasts and upregulated two pathways linked to cell senescence (a biological process associated with cell longevity and an inability to replicate), p53 and p16-retinoblastoma protein pathways. We compared a single exposure of CSE to multiple exposures over an extended time course. A single exposure to CSE led to cell growth inhibition at multiple phases of the cell cycle without killing the cells. The decrease in proliferation was accompanied by increased ATM, p53, and p21 activity. However, several important senescent markers were not present in the cells at an earlier time point. When we examined multiple exposures to CSE, we found that the cells had profound growth arrest, a flat and enlarged morphology, upregulated p16, and senescence-associated β-galactosidase activity, which is consistent with a classic senescent phenotype. These observations suggest that while a single exposure to cigarette smoke inhibits normal fibroblast proliferation (required for lung repair), multiple exposures to cigarette smoke move cells into an irreversible state of senescence. This inability to repair lung injury may be an essential feature of emphysema. PMID:16840774

The biological mechanisms of aging, and more specifically cellularsenescence, are increasingly a subject of research. Cellularsenescence may be a common determinant of many age-related diseases, including some chronic lung diseases such as chronic obstructive pulmonary disease (COPD) or idiopathic pulmonary fibrosis. Many arguments suggest that these diseases are associated with premature senescence of lung cells, which may be involved in the pathophysiology of respiratory alterations. Furthermore, these diseases are associated with systemic manifestations, such as bone loss, muscle wasting and atherosclerosis, which impact on symptoms and prognosis. Whether these alterations are related to a common pathogenic mechanism or develop independently in patients with COPD remains an open question. In this review, we will focus on cellularsenescence and COPD. Two concepts will be discussed: (1) the role of cell senescence in the pathophysiology of lung destruction, vascular remodeling and inflammation in COPD, (2) the possible link between the pulmonary and systemic manifestations of COPD which could reflect a general process of accelerated aging. PMID:25496787

We have studied autumn leaf senescence in a free-growing aspen (Populus tremula) by following changes in pigment, metabolite and nutrient content, photosynthesis, and cell and organelle integrity. The senescence process started on September 11, 2003, apparently initiated solely by the photoperiod, and progressed steadily without any obvious influence of other environmental signals. For example, after this date, senescing leaves accumulated anthocyanins in response to conditions inducing photooxidative stress, but at the beginning of September the leaves did not. Degradation of leaf constituents took place over an 18-d period, and, although the cells in each leaf did not all senesce in parallel, senescence in the tree as a whole was synchronous. Lutein and β-carotene were degraded in parallel with chlorophyll, whereas neoxanthin and the xanthophyll cycle pigments were retained longer. Chloroplasts in each cell were rapidly converted to gerontoplasts and many, although not all, cells died. From September 19, when chlorophyll levels had dropped by 50%, mitochondrial respiration provided the energy for nutrient remobilization. Remobilization seemed to stop on September 29, probably due to the cessation of phloem transport, but, up to abscission of the last leaves (over 1 week later), some cells were metabolically active and had chlorophyll-containing gerontoplasts. About 80% of the nitrogen and phosphorus was remobilized, and on September 29 a sudden change occurred in the δ15n of the cellular content, indicating that volatile compounds may have been released. PMID:16299183

A confounding aspect of biological ageing is the nature and role of senescent cells. It is unclear whether the three major types of cellularsenescence, namely replicative senescence, oncogene-induced senescence and DNA damage-induced senescence are descriptions of the same phenomenon instigated by different sources, or if each of these is distinct, and how they are associated with ageing. Recently, we devised an epigenetic clock with unprecedented accuracy and precision based on very specific DNA methylation changes that occur in function of age. Using primary cells, telomerase-expressing cells and oncogene-expressing cells of the same genetic background, we show that induction of replicative senescence (RS) and oncogene-induced senescence (OIS) are accompanied by ageing of the cell. However, senescence induced by DNA damage is not, even though RS and OIS activate the cellular DNA damage response pathway, highlighting the independence of senescence from cellular ageing. Consistent with this, we observed that telomerase-immortalised cells aged in culture without having been treated with any senescence inducers or DNA-damaging agents, re-affirming the independence of the process of ageing from telomeres and senescence. Collectively, our results reveal that cellular ageing is distinct from cellularsenescence and independent of DNA damage response and telomere length. PMID:26885756

Replicative senescence (RS) that limits the proliferating potential of normal eukaryotic cells occurs either by a cell-division counting mechanism linked to telomere erosion or prematurely through induction by cell stressors such as oncogene hyper-activation. However, there is evidence that RS also occurs by a stochastic process that is independent of number of cell divisions or cellular stress and yet it leads to a highly-stable, non-reversible post-mitotic state that may be long-lasting and that such a process is widely represented among higher eukaryotes. Here I present and discuss evidence that the interactions between DNA and the nuclear substructure, commonly known as the nuclear matrix, define a higher-order structure within the cell nucleus that following thermodynamic constraints, stochastically evolves towards maximum stability, thus becoming limiting for mitosis to occur. It is suggested that this process is responsible for ultimate replicative senescence and yet it is compatible with long-term cell survival. PMID:20157542

Cellularsenescence is defined as permanent cell cycle arrest induced by various stresses. Although the p53 transcriptional activity is essential for senescence induction, the downstream genes that are crucial for senescence remain unsolved. Here, by using a developed experimental system in which cellularsenescence or apoptosis is induced preferentially by altering concentration of etoposide, a DNA-damaging drug, we compared gene expression profiles of senescent and apoptotic cells by microarray analysis. Subtraction of the expression profile of apoptotic cells identified 20 genes upregulated specifically in senescent cells. Furthermore, 6 out of 20 genes showed p53-dependent upregulation by comparing gene expression between p53-proficient and -deficient cells. These 6 genes were also upregulated during replicative senescence of normal human diploid fibroblasts, suggesting that upregulation of these genes is a general phenomenon in senescence. Among these genes, 2 genes (PRODH and DAO) were found to be directly regulated by p53, and ectopic expression of 4 genes (PRODH, DAO, EPN3, and GPR172B) affected senescence phenotypes induced by etoposide treatment. Collectively, our results identified several proteins as novel downstream effectors of p53-mediated senescence and provided new clues for further research on the complex signalling networks underlying the induction and maintenance of senescence. PMID:27545311

Cellularsenescence is defined as permanent cell cycle arrest induced by various stresses. Although the p53 transcriptional activity is essential for senescence induction, the downstream genes that are crucial for senescence remain unsolved. Here, by using a developed experimental system in which cellularsenescence or apoptosis is induced preferentially by altering concentration of etoposide, a DNA-damaging drug, we compared gene expression profiles of senescent and apoptotic cells by microarray analysis. Subtraction of the expression profile of apoptotic cells identified 20 genes upregulated specifically in senescent cells. Furthermore, 6 out of 20 genes showed p53-dependent upregulation by comparing gene expression between p53-proficient and -deficient cells. These 6 genes were also upregulated during replicative senescence of normal human diploid fibroblasts, suggesting that upregulation of these genes is a general phenomenon in senescence. Among these genes, 2 genes (PRODH and DAO) were found to be directly regulated by p53, and ectopic expression of 4 genes (PRODH, DAO, EPN3, and GPR172B) affected senescence phenotypes induced by etoposide treatment. Collectively, our results identified several proteins as novel downstream effectors of p53-mediated senescence and provided new clues for further research on the complex signalling networks underlying the induction and maintenance of senescence. PMID:27545311

Normal human somatic cells have strictly limited proliferative capacity and reach a state of senescence when it becomes exhausted. It is believed that senescence is a response to extensive and irreparable DNA injury, localized in telomeric and/or non-telomeric regions of the genome. Main cause of this damage is oxidative stress, increasing due to deteriorated function of mitochondria. Senescent cells accumulate in tissues during aging, which is causatively linked with the development of various pathologies in elderly individuals, including cancer. This paper, prepared exactly 50 years after Leonard Hayflick's discovery of the relationship between cellularsenescence and organismal aging is aimed at presenting the current knowledge about molecular determinants of senescence, with particular emphasis paid to the role of oxidative stress, effectors of senescence at the level of cell cycle, markers of this phenomenon, and the effect of senescent cells on the development of certain age-related diseases. PMID:27117098

Considerable evidence implicates cellularsenescence in the biology of aging and chronic disease. Diet and exercise are determinants of healthy aging; however, the extent to which they affect the behavior and accretion of senescent cells within distinct tissues is not clear. Here we tested the hypothesis that exercise prevents premature senescent cell accumulation and systemic metabolic dysfunction induced by a fast-food diet (FFD). Using transgenic mice that express EGFP in response to activation of the senescence-associated p16(INK4a) promoter, we demonstrate that FFD consumption causes deleterious changes in body weight and composition as well as in measures of physical, cardiac, and metabolic health. The harmful effects of the FFD were associated with dramatic increases in several markers of senescence, including p16, EGFP, senescence-associated β-galactosidase, and the senescence-associated secretory phenotype (SASP) specifically in visceral adipose tissue. We show that exercise prevents the accumulation of senescent cells and the expression of the SASP while nullifying the damaging effects of the FFD on parameters of health. We also demonstrate that exercise initiated after long-term FFD feeding reduces senescent phenotype markers in visceral adipose tissue while attenuating physical impairments, suggesting that exercise may provide restorative benefit by mitigating accrued senescent burden. These findings highlight a novel mechanism by which exercise mediates its beneficial effects and reinforces the effect of modifiable lifestyle choices on health span. PMID:26983960

Cellularsenescence occurs not only in cultured fibroblasts, but also in undifferentiated and specialized cells from various tissues of all ages, in vitro and in vivo. Here, we review recent findings on the role of cellularsenescence in immune cell fate decisions in macrophage polarization, natural killer cell phenotype, and following T-lymphocyte activation. We also introduce the involvement of the onset of cellularsenescence in some immune responses including T-helper lymphocyte-dependent tissue homeostatic functions and T-regulatory cell-dependent suppressive mechanisms. Altogether, these data propose that cellular senescence plays a wide-reaching role as a homeostatic orchestrator. PMID:26910559

The TOR (target of rapamycin) pathway has been convincingly shown to promote aging in various model organisms. In mice, inhibiting mTOR (mammalian TOR) by rapamycin treatment later in life can significantly extend lifespan and mitigate multiple age-related diseases. However, the underlying mechanisms are poorly understood. Cellularsenescence is strongly correlated to organismal aging therefore providing an attractive model to examine the mechanisms by which mTOR inhibition contributes to longevity and delaying the onset of related diseases. In this review, we examine the connections between mTOR and cellularsenescence and discuss how understanding cellularsenescence on the aspect of mTOR signaling may help to fully appreciate its role in the organismal aging. We also highlight the opposing roles of senescence in various human diseases and discuss the caveats in interpreting the emerging experimental data. PMID:25110610

Vitamin E is an important antioxidant that protects cells from oxidative stress-induced damage, which is an important contributor to the progression of ageing. Ageing can be studied in vitro using primary cells reaching a state of irreversible growth arrest called senescence after a limited number of cellular divisions. Generally, the most utilized biomarker of senescence is represented by the expression of the senescence associated β-galactosidase (SA-β-gal). We aimed here to study the possible effects of vitamin E supplementation in two different human primary cell types (HUVECs and fibroblasts) during the progression of cellularsenescence. Utilizing an unbiased automated system, based on the detection of the SA-β-gal, we quantified cellularsenescence in vitro and showed that vitamin E supplementation reduced the numbers of senescent cells during progression of ageing. Acute vitamin E supplementation did not affect cellular proliferation, whereas it was decreased after chronic treatment. Mechanistically, we show that vitamin E supplementation acts through downregulation of the expression of the cycline dependent kinase inhibitor P21. The data obtained from this study support the antiageing properties of vitamin E and identify possible mechanisms of action that warrant further investigation. PMID:26613084

Vitamin E is an important antioxidant that protects cells from oxidative stress-induced damage, which is an important contributor to the progression of ageing. Ageing can be studied in vitro using primary cells reaching a state of irreversible growth arrest called senescence after a limited number of cellular divisions. Generally, the most utilized biomarker of senescence is represented by the expression of the senescence associated β-galactosidase (SA-β-gal). We aimed here to study the possible effects of vitamin E supplementation in two different human primary cell types (HUVECs and fibroblasts) during the progression of cellularsenescence. Utilizing an unbiased automated system, based on the detection of the SA-β-gal, we quantified cellularsenescence in vitro and showed that vitamin E supplementation reduced the numbers of senescent cells during progression of ageing. Acute vitamin E supplementation did not affect cellular proliferation, whereas it was decreased after chronic treatment. Mechanistically, we show that vitamin E supplementation acts through downregulation of the expression of the cycline dependent kinase inhibitor P21. The data obtained from this study support the antiageing properties of vitamin E and identify possible mechanisms of action that warrant further investigation. PMID:26613084

Cells continually experience stress and damage from exogenous and endogenous sources, and their responses range from complete recovery to cell death. Proliferating cells can initiate an additional response by adopting a state of permanent cell-cycle arrest that is termed cellularsenescence. Understanding the causes and consequences of cellularsenescence has provided novel insights into how cells react to stress, especially genotoxic stress, and how this cellular response can affect complex organismal processes such as the development of cancer and ageing. PMID:17667954

Cellularsenescence is thought to play a major role in age-related diseases, which cause nearly 67% of all human deaths worldwide. Recent research in mice showed that exercising mice had higher levels of telomerase, an enzyme that helps maintain telomere length, than nonexercising mice. A commonly used model for biological aging was proposed by Penna. I propose a modification of the Penna model that incorporates cellularsenescence and find an analytical steady-state solution following Coe, Mao, and Cates [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.89.288103 89, 288103 (2002)]. I find that models corresponding to delayed cellularsenescence have younger populations that live longer. I fit the model to the United Kingdom's death distribution, which the original Penna model cannot do.

Population aging simultaneously highlights the remarkable advances in science, medicine, and public policy, and the formidable challenges facing society. Indeed, aging is the primary risk factor for many of the most common chronic diseases and frailty, which result in profound social and economic costs. Population aging also reveals an opportunity, i.e. interventions to disrupt the fundamental biology of aging could significantly delay the onset of age-related conditions as a group, and, as a result, extend the healthy life span, or health span. There is now considerable evidence that cellularsenescence is an underlying mechanism of aging and age-related conditions. Cellularsenescence is a process in which cells lose the ability to divide and damage neighboring cells by the factors they secrete, collectively referred to as the senescence-associated secretory phenotype (SASP). Herein, we discuss the concept of cellularsenescence, review the evidence that implicates cellularsenescence and SASP in age-related deterioration, hyperproliferation, and inflammation, and propose that this underlying mechanism of aging may play a fundamental role in the biology of frailty. PMID:26485647

Cellularsenescence is defined as the physiological program of terminal growth arrest, which can be triggered by various endogenous or exogenous stress signals. Cellularsenescence can be induced in response to oncogenic activation and acts as a barrier to tumorigenesis. Moreover, tumor cells can undergo senescence when exposed to chemotherapeutic agents. In addition to suppressing tumorigenesis, senescent cells remain metabolically active and may contribute to tumor formation and to therapy resistance. In the current review, we discuss the molecular regulation of cellularsenescence, the potential implications of senescence in human cancers, and the possibility of exploiting cellularsenescence for the treatment of cancers. PMID:21909124

Alteration of seasonal phenology cues due to climate change has led to changes in the onset and duration of the growing season. While photoperiod often acts as an ultimate control on phenological events, recent studies have shown that environmental cues such as temperature and soil water content can modify the direction and rate of senescence processes. Warmer temperatures have resulted in an observed trend towards delayed senescence across temperate latitudes. However, Arctic regions are characterized by extreme seasonality and rapidly decreasing photoperiod, and consequently senescence may not shift as climate warms. We monitored the timing of Arctic plant community senescence for three years under the framework of an experimental manipulation that altered seasonal phenological cues through warming and earlier snowmelt. Alternative models of senescence were tested to determine if microclimate (air temperature, soil temperature, and soil moisture) or start of season phenology affect the timing and rate of community senescence. We found that all three microclimate predictors contributed to explaining variation in timing of senescence, suggesting that photoperiod is not the sole control on timing of senescence in Arctic plant communities. Rather, increased air and soil temperatures along with drier soil conditions, led to acceleration in the onset of senescence at a community level. Our data suggest that (1) multiple climate drivers predict timing of plant community senescence, and (2) climate change could result in a shorter peak season due to earlier onset of senescence, which would decrease the potential carbon uptake in moist acidic tundra.

In this paper we present cellularsenescence as the ultimate driver of the aging process, as a “causal nexus” that bridges microscopic subcellular damage with the phenotypic, macroscopic effect of aging. It is important to understand how the various types of subcellular damage correlated with the aging process lead to the larger, visible effects of anatomical aging. While it has always been assumed that subcellular damage (cause) results in macroscopic aging (effect), the bridging link between the two has been hard to define. Here, we propose that this bridge, which we term the “causal nexus”, is in fact cellularsenescence. The subcellular damage itself does not directly cause the visible signs of aging, but rather, as the damage accumulates and reaches a critical mass, cells cease to proliferate and acquire the deleterious “senescence-associated secretory phenotype” (SASP) which then leads to the macroscopic consequences of tissue breakdown to create the physiologically aged phenotype. Thus senescence is a precondition for anatomical aging, and this explains why aging is a gradual process that remains largely invisible during most of its progression. The subcellular damage includes shortening of telomeres, damage to mitochondria, aneuploidy, and DNA double-strand breaks triggered by various genetic, epigenetic, and environmental factors. Damage pathways acting in isolation or in concert converge at the causal nexus of cellularsenescence. In each species some types of damage can be more causative than in others and operate at a variable pace; for example, telomere erosion appears to be a primary cause in human cells, whereas activation of tumor suppressor genes is more causative in rodents. Such species-specific mechanisms indicate that despite different initial causes, most of aging is traced to a single convergent causal nexus: senescence. The exception is in some invertebrate species that escape senescence, and in non-dividing cells such as neurons

In this paper we present cellularsenescence as the ultimate driver of the aging process, as a "causal nexus" that bridges microscopic subcellular damage with the phenotypic, macroscopic effect of aging. It is important to understand how the various types of subcellular damage correlated with the aging process lead to the larger, visible effects of anatomical aging. While it has always been assumed that subcellular damage (cause) results in macroscopic aging (effect), the bridging link between the two has been hard to define. Here, we propose that this bridge, which we term the "causal nexus", is in fact cellularsenescence. The subcellular damage itself does not directly cause the visible signs of aging, but rather, as the damage accumulates and reaches a critical mass, cells cease to proliferate and acquire the deleterious "senescence-associated secretory phenotype" (SASP) which then leads to the macroscopic consequences of tissue breakdown to create the physiologically aged phenotype. Thus senescence is a precondition for anatomical aging, and this explains why aging is a gradual process that remains largely invisible during most of its progression. The subcellular damage includes shortening of telomeres, damage to mitochondria, aneuploidy, and DNA double-strand breaks triggered by various genetic, epigenetic, and environmental factors. Damage pathways acting in isolation or in concert converge at the causal nexus of cellularsenescence. In each species some types of damage can be more causative than in others and operate at a variable pace; for example, telomere erosion appears to be a primary cause in human cells, whereas activation of tumor suppressor genes is more causative in rodents. Such species-specific mechanisms indicate that despite different initial causes, most of aging is traced to a single convergent causal nexus: senescence. The exception is in some invertebrate species that escape senescence, and in non-dividing cells such as neurons, where

Currently, the oxidative stress (or free radical) theory of aging is the most popular explanation of how aging occurs at the molecular level. Accordingly, a stress-induced senescence-like phenotype of human dermal fibroblasts can be induced in vitro by the exposure of human diploid fibroblasts to subcytotoxic concentrations of hydrogen peroxide. However, several biomarkers of replicative senescence e.g. cell cycle arrest and enlarged morphology are abrogated 14 days after treatment, indicating that reactive oxygen species (ROS) rather acts as a trigger for short-term senescence (1-3 days) than being responsible for the maintenance of the senescence-like phenotype. Further, DNA-damaging factors are discussed resulting in a permanent senescent cell type. To induce long-term premature senescence and to understand the molecular alterations occurring during the aging process, we analyzed mitomycin C (MMC) as an alkylating DNA-damaging agent and ROS producer. Human dermal fibroblasts (HDF), used as model for skin aging, were exposed to non-cytotoxic concentrations of MMC and analyzed for potential markers of cellular aging, for example enlarged morphology, activity of senescence-associated-ß-galactosidase, cell cycle arrest, increased ROS production and MMP1-activity, which are well-documented for HDF in replicative senescence. Our data show that mitomycin C treatment results in a drug-induced acceleratedsenescence (DIAS) with long-term expression of senescence markers, demonstrating that a combination of different susceptibility factors, here ROS and DNA alkylation, are necessary to induce a permanent senescent cell type. PMID:24833306

The Senescence-Accelerated Mouse (SAM) has been under development by our research team at Kyoto University since 1970 through the selective inbreeding of the AKR/J strain of mice donated by the Jackson Laboratory in 1968, based on a graded score for senescence, life span, and pathologic phenotype. At present, there are 12 lines of SAM: nine senescence-prone inbred strains (SAMP) including SAMP1, SAMP2, SAMP3, SAMP6, SAMP7, SAMP8, SAMP9, SAMP10, and SAMP11; and three senescence-resistant inbred strains (SAMR) including SAMR1, SAMR4, and SAMR5. Data from survival curves, Gompertzian function, and grading score of senescence, together with growth patterns of body weight of these SAMP and SAMR, revealed that the characteristic feature of aging common to all SAMP mice is "acceleratedsenescence;" early onset and irreversible advance of senescence manifested by several signs and gross lesions such as the loss of normal behavior, various skin lesions, increased lordokyphosis, etc., after a period of normal development. In the course of SAM development, it became evident that SAMP strains manifest various pathologic phenotypes that are characteristic enough to differentiate the SAM strains. The genetic background and significance of SAM development are discussed. PMID:9088907

Cellularsenescence is a stable cell cycle arrest, caused by insults, such as: telomere erosion, oncogene activation, irradiation, DNA damage, oxidative stress, and viral infection. Extrinsic stimuli such as cell culture stress can also trigger this growth arrest. Senescence is thought to have evolved as an example of antagonistic pleiotropy, as it acts as a tumor suppressor mechanism during the reproductive age, but can promote organismal aging by disrupting tissue renewal, repair, and regeneration later in life. The mechanisms underlying the senescence growth arrest are broadly considered to involve p16INK4A-pRB and p53-p21CIP1/WAF1/SDI1 tumor suppressor pathways; but it is not known what makes the senescence arrest stable and what the critical downstream targets are, as they are likely to be key to the establishment and maintenance of the senescent state. MYB-related protein B (B-MYB/MYBL2), a member of the myeloblastosis family of transcription factors, has recently emerged as a potential candidate for regulating entry into senescence. Here, we review the evidence which indicates that loss of B-MYB expression has an important role in causing senescence growth arrest. We discuss how B-MYB acts, as the gatekeeper, to coordinate transit through the cell cycle, in conjunction with the multivulval class B (MuvB) complex and FOXM1 transcription factors. We also evaluate the evidence connecting B-MYB to the mTOR nutrient signaling pathway and suggest that inhibition of this pathway leading to an extension of healthspan may involve activation of B-MYB. PMID:24981831

KRAS mutant lung cancers are generally refractory to chemotherapy as well targeted agents. To date, the identification of drugs to therapeutically inhibit K-RAS have been unsuccessful, suggesting that other approaches are required. We demonstrate in both a novel transgenic mutant Kras lung cancer mouse model and in human lung tumors that the inhibition of Twist1 restores a senescence program inducing the loss of a neoplastic phenotype. The Twist1 gene encodes for a transcription factor that is essential during embryogenesis. Twist1 has been suggested to play an important role during tumor progression. However, there is no in vivo evidence that Twist1 plays a role in autochthonous tumorigenesis. Through two novel transgenic mouse models, we show that Twist1 cooperates with KrasG12D to markedly accelerate lung tumorigenesis by abrogating cellularsenescence programs and promoting the progression from benign adenomas to adenocarcinomas. Moreover, the suppression of Twist1 to physiological levels is sufficient to cause Kras mutant lung tumors to undergo senescence and lose their neoplastic features. Finally, we analyzed more than 500 human tumors to demonstrate that TWIST1 is frequently overexpressed in primary human lung tumors. The suppression of TWIST1 in human lung cancer cells also induced cellularsenescence. Hence, TWIST1 is a critical regulator of cellularsenescence programs, and the suppression of TWIST1 in human tumors may be an effective example of pro-senescence therapy. PMID:22654667

Replicative cellularsenescence is a fundamental biological process characterized by an irreversible arrest of proliferation. Senescent cells accumulate a variety of epigenetic changes, but the three-dimensional (3D) organization of their chromatin is not known. We applied a combination of whole-genome chromosome conformation capture (Hi-C), fluorescence in situ hybridization, and in silico modeling methods to characterize the 3D architecture of interphase chromosomes in proliferating, quiescent, and senescent cells. Although the overall organization of the chromatin into active (A) and repressive (B) compartments and topologically associated domains (TADs) is conserved between the three conditions, a subset of TADs switches between compartments. On a global level, the Hi-C interaction matrices of senescent cells are characterized by a relative loss of long-range and gain of short-range interactions within chromosomes. Direct measurements of distances between genetic loci, chromosome volumes, and chromatin accessibility suggest that the Hi-C interaction changes are caused by a significant reduction of the volumes occupied by individual chromosome arms. In contrast, centromeres oppose this overall compaction trend and increase in volume. The structural model arising from our study provides a unique high-resolution view of the complex chromosomal architecture in senescent cells. PMID:26989773

Long-term graft survival after kidney transplantation remains unsatisfactory and unpredictable. Interstitial fibrosis and tubular atrophy are major contributors to late graft loss; features of tubular cell senescence, such as increased p16(INK4a) expression, associate with these tubulointerstitial changes, but it is unknown whether the relationship is causal. Here, loss of the INK4a locus in mice, which allows escape from p16(INK4a)-dependent senescence, significantly reduced interstitial fibrosis and tubular atrophy and associated with improved renal function, conservation of nephron mass, and transplant survival. Compared with wild-type controls, kidneys from INK4a(-/-) mice developed significantly less interstitial fibrosis and tubular atrophy after ischemia-reperfusion injury. Consistently, mice that received kidney transplants from INK4a/ARF(-/-) donors had significantly better survival 21 days after life-supporting kidney transplantation and developed less tubulointerstitial changes. This correlated with higher proliferative rates of tubular cells and significantly fewer senescent cells. Taken together, these data suggest a pathogenic role of renal cellularsenescence in the development of interstitial fibrosis and tubular atrophy and kidney graft deterioration by preventing the recovery from injury. Inhibiting premature senescence could have therapeutic benefit in kidney transplantation but has to be balanced against the risks of suspending antitumor defenses. PMID:22797186

Sirtuin1 (SIRT1) regulates inflammation, aging (lifespan and healthspan), calorie restriction/energetics, mitochondrial biogenesis, stress resistance, cellularsenescence, endothelial functions, apoptosis/autophagy, and circadian rhythms through deacetylation of transcription factors and histones. SIRT1 level and activity are decreased in chronic inflammatory conditions and aging where oxidative stress occurs. SIRT1 is regulated by a NAD+-dependent DNA repair enzyme poly(ADP-ribose)-polymerase-1 (PARP-1), and subsequent NAD+ depletion by oxidative stresses may have consequent effects on inflammatory and stress responses as well as cellularsenescence. SIRT1 has been shown to undergo covalent oxidative modifications by cigarette smoke-derived oxidants/aldehydes, leading to post-translational modifications, inactivation, and protein degradation. Furthermore, oxidant/carbonyl stress-mediated reduction of SIRT1 leads to the loss of its control on acetylation of target proteins including p53, RelA/p65 and FOXO3, thereby enhancing the inflammatory, pro-senescent and apoptotic responses, as well as endothelial dysfunction. In this review, the mechanisms of cigarette smoke/oxidant-mediated redox post-translational modifications of SIRT1 and its role in PARP1, NF-κB activation, FOXO3 and eNOS regulation, as well as chromatin remodeling/histone modifications during inflammaging are discussed. Furthermore, we also discussed various novel ways to activate SIRT1 either directly or indirectly, which may have therapeutic potential in attenuating inflammation and premature senescence involved in chronic lung diseases. PMID:23542362

The study of cellularsenescence and proliferative lifespan is becoming increasingly important because of the promises of autologous cell therapy, the need for model systems for tissue disease and the implication of senescent cell phenotypes in organismal disease states such as sarcopenia, diabetes and various cancers, among others. Here, we explain the concepts of proliferative cellular lifespan and cellularsenescence, and we present factors that have been shown to mediate cellular lifespan positively or negatively. We review much recent literature and present potential molecular mechanisms by which lifespan mediation occurs, drawing from the fields of telomere biology, metabolism, NAD(+) and sirtuin biology, growth factor signaling and oxygen and antioxidants. We conclude that cellular lifespan and senescence are complex concepts that are governed by multiple independent and interdependent pathways, and that greater understanding of these pathways, their interactions and their convergence upon specific cellular phenotypes may lead to viable therapies for tissue regeneration and treatment of age-related pathologies, which are caused by or exacerbated by senescent cells in vivo. PMID:27417120

Half a century is fast approaching since Hayflick and colleagues formally described the limited ability of normal human cells to proliferate in culture (Hayflick and Moorhead, 1961). This finding--that normal somatic cells, in contrast to cancer cells, cannot divide indefinitely--challenged the prevailing idea that cells from mortal multicellular organisms were intrinsically ''immortal'' (Carrell, 1912). It also spawned two hypotheses, essential elements of which persist today. The first held that the restricted proliferation of normal cells, now termed cellularsenescence, suppresses cancer (Hayflick, 1965; Sager, 1991; Campisi, 2001). The second hypothesis, as explained in the article by Lorenzini et al., suggested that the limited proliferation of cells in culture recapitulated aspects of organismal aging (Hayflick, 1965; Martin, 1993). How well have these hypotheses weathered the ensuing decades? Before answering this question, we first consider current insights into the causes and consequences of cellularsenescence. Like Lorenzini et al., we limit our discussion to mammals. We also focus on fibroblasts, the cell type studied by Lorenzini et al., but consider other types as well. We suggest that replicative capacity in culture is not a straightforward assessment, and that it correlates poorly with both longevity and body mass. We speculate this is due to the malleable and variable nature of replicative capacity, which renders it an indirect metric of qualitative and quantitative differences among cells to undergo senescence, a response that directly alters cellular phenotype and might indirectly alter tissue structure and function.

The Senescence-Accelerated Mouse (SAM) strains are unique and appropriate models for genetic studies on aging because the SAMP strains have an "acceleratedsenescence" phenotype for which the SAMR strains are controls, and each SAMP strain has a strain-specific age-associated disorder. Furthermore, because they have gone through sufficient generations of sister-brother mating, they can be considered inbred strains, which can be analyzed genetically. There are now 11 SAMP strains and 3 SAMR strains descended from the progenitor litters. Analysis with the Gompertz function shows that the SAMP strains have the same initial mortality rate (IMR) as the SAMR strains but a shorter mortality rate doubling time (MRDT), presumably due to genes that accelerated the rate of senescence in the SAMP strains. This acceleratedsenescence may also occur in cultured fibroblast-like cells. We performed molecular genetic characterization of all the SAM strains to acquire a base of genetic information from which we could develop hypotheses on the mechanism of development of SAM strains and genetic factors that contribute to acceleratedsenescence. PMID:9088910

Cellularsenescence, an irreversible cell cycle arrest induced by a diversity of stimuli, has been considered as an innate tumor suppressing mechanism with implications and applications in cancer therapy. Using a targeted proteomics approach we show that fibroblasts induced into senescence by expression of oncogenic Ras exhibit a decrease of global acetylation on all core histones, consistent with formation of senescence-associated heterochromatic foci. We also detected clear increases in repressive markers (e.g., >50% elevation of H3K27me2/3) along with decreases in histone marks associated with increased transcriptional expression/elongation (e.g., H3K36me2/3). Despite the increases in repressive marks of chromatin, 179 loci (of 2206 total) were found to be upregulated by global quantitative proteomics. The changes in the cytosolic proteome indicated an upregulation of mitochondrial proteins and downregulation of proteins involved in glycolysis. These alterations in primary metabolism are opposite of the well-known Warburg effect observed in cancer cells. This study significantly improves our understanding of stress-induced senescence and provides a potential application for triggering it in anti-proliferative strategies that target the primary metabolism in cancer cells. PMID:23798001

The SAM strain of mice is actually a group of related inbred strains consisting of a series of SAMP (acceleratedsenescence-prone) and SAMR (acceleratedsenescence-resistant) strains. Compared with the SAMR strains, the SAMP strains show a more acceleratedsenescence process, a shorter lifespan, and an earlier onset and more rapid progress of age-associated pathological phenotypes similar to human geriatric disorders. The higher oxidative stress status observed in SAMP mice is partly caused by mitochondrial dysfunction, and may be a cause of this senescenceacceleration and age-dependent alterations in cell structure and function. Based on our recent observations, we discuss a possible mechanism for mitochondrial dysfunction resulting in the excessive production of reactive oxygen species, and a role for the hyperoxidative stress status in neurodegeneration in SAMP mice. These SAM strains can serve as a useful tool to understand the cellular mechanisms of age-dependent degeneration, and to develop clinical interventions. PMID:18688709

Senescence of retinal pigment epithelium (RPE) cells is a major contributor to age‑related macular degeneration (AMD). However, the molecular mechanisms underlying RPE dysfunction are not well understood. Apoptosis related protein 3 (Apr3) was originally cloned from HL‑60 cells induced by all‑trans retinoic acid (ATRA). Preliminary data revealed elevated Apr3 expression in the tissues of aged mice, suggesting that it is involved in the aging process. The present study demonstrated that Apr3 mRNA and protein levels were markedly increased in aged mouse RPE cells. Elevated Apr3 expression was also observed during premature senescence induced by oxidative stress (H2O2 and tert‑BHP) in ARPE‑19 cells. Moreover, Apr3 overexpression promoted cellularsenescence in ARPE‑19 cells, as characterized by enhanced senescence‑associated β‑galactosidase activity, reduced cell proliferation and increased expression of the senescence markers p53 and p21. In addition, it was demonstrated that overexpression of Apr3‑N, a truncated counterpart of Apr3, abrogated Apr3‑induced phenotypes. It was concluded that Apr3 expression was induced in replicative and premature senescence of RPE cells and its overexpression acceleratedsenescence of ARPE‑19 cells, which provides important insights into the function of Apr3 in senescence‑associated diseases. PMID:26934949

Cellularsenescence is a process that results from a variety of stresses, leading to a state of irreversible growth arrest. Senescent cells accumulate during aging and have been implicated in promoting a variety of age-related diseases. Mitochondrial stress is an effective inducer of cellularsenescence, but the mechanisms by which mitochondria regulate permanent cell growth arrest are largely unexplored. Here, we review some of the mitochondrial signaling pathways that participate in establishing cellularsenescence. We discuss the role of mitochondrial reactive oxygen species (ROS), mitochondrial dynamics (fission and fusion), the electron transport chain (ETC), bioenergetic balance, redox state, metabolic signature, and calcium homeostasis in controlling cellular growth arrest. We emphasize that multiple mitochondrial signaling pathways, besides mitochondrial ROS, can induce cellularsenescence. Together, these pathways provide a broader perspective for studying the contribution of mitochondrial stress to aging, linking mitochondrial dysfunction and aging through the process of cellularsenescence. PMID:25399755

Cellularsenescence is a process that results from a variety of stresses, leading to a state of irreversible growth arrest. Senescent cells accumulate during aging and have been implicated in promoting a variety of age-related diseases. Mitochondrial stress is an effective inducer of cellularsenescence, but the mechanisms by which mitochondria regulate permanent cell growth arrest are largely unexplored. Here, we review some of the mitochondrial signaling pathways that participate in establishing cellularsenescence. We discuss the role of mitochondrial reactive oxygen species (ROS), mitochondrial dynamics (fission and fusion), the electron transport chain (ETC), bioenergetic balance, redox state, metabolic signature, and calcium homeostasis in controlling cellular growth arrest. We emphasize that multiple mitochondrial signaling pathways, besides mitochondrial ROS, can induce cellularsenescence. Together, these pathways provide a broader perspective for studying the contribution of mitochondrial stress to aging, linking mitochondrial dysfunction and aging through the process of cellularsenescence. PMID:25399755

Senescence is a highly regulated process characterized by the active breakdown of cells, which ultimately leads to the death of plant organs or whole plants. In annual plants such as Arabidopsis thaliana senescence can be observed in each individual leaf. Whether deficiencies in photosynthesis promote the induction of senescence was investigated by monitoring chlorophyll degradation, photosynthetic parameters, and reactive oxygen species accumulation in photosynthetic mutants. Several mutations affecting components of the photosynthetic apparatus, including psal-2, psan-2, and psbs, were found to lead to premature or faster senescence, as did simultaneous inactivation of the STN7 and STN8 kinases. Premature senescence is apparently not directly linked to an overall reduction in photosynthesis but to perturbations in specific aspects of the process. Dark-induced senescence is accelerated in mutants affected in linear electron flow, especially psad2-1, psan-2, and pete2-1, as well as in stn7 and stn8 mutants and STN7 and STN8 overexpressor lines. Interestingly, no direct link with ROS production could be observed. PMID:26272903

Cellularsenescence, a process that imposes permanent proliferative arrest on cells in response to various stressors, has emerged as a potentially important contributor to aging and age-related disease, and it is an attractive target for therapeutic exploitation. A wealth of information about senescence in cultured cells has been acquired over the past half century; however, senescence in living organisms is poorly understood, largely because of technical limitations relating to the identification and characterization of senescent cells in tissues and organs. Furthermore, newly recognized beneficial signaling functions of senescence suggest that indiscriminately targeting senescent cells or modulating their secretome for anti-aging therapy may have negative consequences. Here we discuss current progress and challenges in understanding the stressors that induce senescence in vivo, the cell types that are prone to senesce, and the autocrine and paracrine properties of senescent cells in the contexts of aging and age-related diseases as well as disease therapy. PMID:26646499

XFE progeroid syndrome, a disease of accelerated aging caused by deficiency in the DNA repair endonuclease XPF-ERCC1, is modeled by Ercc1 knockout and hypomorphic mice. Tissues and primary cells from these mice senesce prematurely, offering a unique opportunity to identify factors that regulate senescence and aging. We compared microRNA (miRNA) expression in Ercc1−/− primary mouse embryonic fibroblasts (MEFs) and wild-type (WT) MEFs in different growth conditions to identify miRNAs that drive cellularsenescence. Microarray analysis showed three differentially expressed miRNAs in passage 7 (P7) Ercc1−/− MEFs grown at 20% O2 compared to Ercc1−/− MEFs grown at 3% O2. Thirty-six differentially expressed miRNAs were identified in Ercc1−/− MEFs at P7 compared to early passage (P3) in 3% O2. Eight of these miRNAs (miR-449a, miR-455*, miR-128, miR-497, miR-543, miR-450b-3p, miR-872 and miR-10b) were similarly downregulated in the liver of progeroid Ercc1−/Δ and old WT mice compared to adult WT mice, a tissue that senesces with aging. Three miRNAs (miR-449a, miR-455* and miR-128) were also downregulated in Ercc1−/Δ and WT old mice kidneys compared to young WT mice. We also discovered that the miRNA expression regulator Dicer is significantly downregulated in tissues of old mice and late passage cells compared to young controls. Collectively these results support the conclusion that the miRNAs identified may play an important role in staving off cellularsenescence and their altered expression could be indicative of aging. PMID:23852002

A variety of short-lived mouse strains (SAMP strains) and control strains of less abbreviated life span (SAMR strains) have been proposed as murine models of acceleratedsenescence. Each SAMP strain, in addition to displaying "progeroid" traits of accelerated aging, exhibits a singular age-related pathology. The application of this animal model to the study of normal aging processes has been and remains controversial. Therefore, we have undertaken a study of dermal fibroblasts derived from the short-lived SAMP6 strain, which shows early-onset and progressive osteopenia. We have investigated cellular and molecular characteristics that are associated with in vitro aging of normal human fibroblasts, and which are exacerbated in fibroblasts from patients with Werner syndrome, a human model of premature senescence. We found that SAMP6 dermal fibroblasts, relative to SAMR1 and C57BL/6 controls, exhibit characteristics of premature or acceleratedcellularsenescence with regard to in vitro life span, initial growth rate, and patterns of gene expression. PMID:9402934

Cell senescence is associated with the secretion of many factors, the so-called "senescence-associated secretory phenotype", which may alter tissue microenvironment, stimulating the organism to clean up senescent cells and replace them with newly divided ones. Therefore, although no longer dividing, these cells are still metabolically active and influence the surrounding tissue. Much attention has been recently focused not only on soluble factors released by senescent cells, but also on extracellular vesicles as conveyors of senescence signals outside the cell. Here, we give an overview of the role of extracellular vesicles in biological processes and signaling pathways related to senescence and aging. PMID:27571072

Cellularsenescence is a complex stress response that permanently arrests the proliferation of cells at risk for oncogenic transformation. However, senescent cells can also drive phenotypes associated with aging. Although the senescence-associated growth arrest prevents the development of cancer, and the metabolism of cancer cells has been studied in depth, the metabolic causes and consequences of cellularsenescence were largely unexplored until recently. New findings reveal key roles for several aspects of cellular metabolism in the establishment and control of senescent phenotypes. These discoveries have important implications for both cancer and aging. In this review, we highlight some of the recent links between metabolism and phenotypes that are commonly associated with senescent cells. PMID:27304503

Autophagy is triggered in vascular smooth muscle cells (VSMCs) of diseased arterial vessels. However, the role of VSMC autophagy in cardiovascular disease is poorly understood. Therefore, we investigated the effect of defective autophagy on VSMC survival and phenotype and its significance in the development of postinjury neointima formation and atherosclerosis. Tissue-specific deletion of the essential autophagy gene Atg7 in murine VSMCs (atg7−/− VSMCs) caused accumulation of SQSTM1/p62 and accelerated the development of stress-induced premature senescence as shown by cellular and nuclear hypertrophy, CDKN2A-RB-mediated G1 proliferative arrest and senescence-associated GLB1 activity. Transfection of SQSTM1-encoding plasmid DNA in Atg7+/+ VSMCs induced similar features, suggesting that accumulation of SQSTM1 promotes VSMC senescence. Interestingly, atg7−/− VSMCs were resistant to oxidative stress-induced cell death as compared to controls. This effect was attributed to nuclear translocation of the transcription factor NFE2L2 resulting in upregulation of several antioxidative enzymes. In vivo, defective VSMC autophagy led to upregulation of MMP9, TGFB and CXCL12 and promoted postinjury neointima formation and diet-induced atherogenesis. Lesions of VSMC-specific atg7 knockout mice were characterized by increased total collagen deposition, nuclear hypertrophy, CDKN2A upregulation, RB hypophosphorylation, and GLB1 activity, all features typical of cellularsenescence. To conclude, autophagy is crucial for VSMC function, phenotype, and survival. Defective autophagy in VSMCs acceleratessenescence and promotes ligation-induced neointima formation and diet-induced atherogenesis, implying that autophagy inhibition as therapeutic strategy in the treatment of neointimal stenosis and atherosclerosis would be unfavorable. Conversely, stimulation of autophagy could be a valuable new strategy in the treatment of arterial disease. PMID:26391655

5-Bromodeoxyuridine (BrdU), a thymidine analogue, induces cellularsenescence in mammalian cells. BrdU induces cellularsenescence probably through the regulation of chromatin because BrdU destabilizes or disrupts nucleosome positioning and decondenses heterochromatin. Since heterochromatin is tethered to the nuclear periphery through the interaction with the nuclear envelope proteins, we examined the localization of the several nuclear envelope proteins such as lamins, lamin-interacting proteins, nuclear pore complex proteins, and nuclear transport proteins in senescent cells. We have shown here that lamin B receptor (LBR) showed a change in localization in both BrdU-induced and replicative senescent cells. PMID:27059139

Highlights: Black-Right-Pointing-Pointer Cellularsenescence plays an important role in tumorigenesis and aging process. Black-Right-Pointing-Pointer We demonstrated IGF-I enhanced cellularsenescence in primary confluent cells. Black-Right-Pointing-Pointer IGF-I enhanced cellularsenescence in the ROS and p53-dependent manner. Black-Right-Pointing-Pointer These results may explain the underlying mechanisms of IGF-I involvement in tumorigenesis and in regulation of aging. -- Abstract: Cellularsenescence is characterized by growth arrest, enlarged and flattened cell morphology, the expression of senescence-associated {beta}-galactosidase (SA-{beta}-gal), and by activation of tumor suppressor networks. Insulin-like growth factor-I (IGF-I) plays a critical role in cellular growth, proliferation, tumorigenesis, and regulation of aging. In the present study, we show that IGF-I enhances cellularsenescence in mouse, rat, and human primary cells in the confluent state. IGF-I induced expression of a DNA damage marker, {gamma}H2AX, the increased levels of p53 and p21 proteins, and activated SA-{beta}-gal. In the confluent state, an altered downstream signaling of IGF-I receptor was observed. Treatment with a reactive oxygen species (ROS) scavenger, N-acetylcystein (NAC) significantly suppressed induction of these markers, indicating that ROS are involved in the induction of cellularsenescence by IGF-I. In p53-null mouse embryonic fibroblasts, the IGF-I-induced augmentation of SA-{beta}-gal and p21 was inhibited, demonstrating that p53 is required for cellularsenescence induced by IGF-I. Thus, these data reveal a novel pathway whereby IGF-I enhances cellularsenescence in the ROS and p53-dependent manner and may explain the underlying mechanisms of IGF-I involvement in tumorigenesis and in regulation of aging.

Dental stem cells such as human dental follicle cells (DFCs) have opened new promising treatment alternatives for today's dental health issues such as periodontal tissue regeneration. However, cellularsenescence represents a restricting factor to cultured stem cells, resulting in limited lifespan and reduced cell differentiation potential. Therefore, this study evaluated if and how DFCs exhibit features of cellularsenescence after being expanded in cell culture. The cell proliferation of DFCs decreased, while the cell size increased during prolonged cell culture. Moreover, DFCs expressed the senescence-associated β-galactosidase after a prolonged cell culture. The onset of senescence inhibited both the induction of osteoblast markers RUNX2 and osteopontin and the biomineralization of DFCs after stimulation of the osteogenic differentiation. In conclusion, we showed that a prolonged cell culture induces cellularsenescence and inhibits the osteogenic differentiation in DFCs. PMID:27165403

During leaf senescence, degradation of chloroplasts precede to changes in nuclei and other cytoplasmic organelles, RuBisCO stability is progressively lost, grana lose their structure, plastidial DNA becomes distorted and degraded, the number of plastoglobuli increases and abundant senescence-associated vesicles containing electronically dense particles emerge from chloroplasts pouring their content into the central vacuole. This study examines quinoa leaf tissues during development and senescence using a range of well-established markers of programmed cell death (PCD), including: morphological changes in nuclei and chloroplasts, degradation of RuBisCO, changes in chlorophyll content, DNA degradation, variations in ploidy levels, and changes in nuclease profiles. TUNEL reaction and DNA electrophoresis demonstrated that DNA fragmentation in nuclei occurs at early senescence, which correlates with induction of specific nucleases. During senescence, metabolic activity is high and nuclei endoreduplicate, peaking at 4C. At this time, TEM images showed some healthy nuclei with condensed chromatin and nucleoli. We have found that DNA fragmentation, induction of senescence-associated nucleases and endoreduplication take place during leaf senescence. This provides a starting point for further research aiming to identify key genes involved in the senescence of quinoa leaves. PMID:26259186

Epigenomic modification plays important roles in regulating gene expression during development, differentiation, and cellularsenescence. When oncogenes are activated, cells fall into stable growth arrest to block cellular proliferation, which is called oncogene-induced senescence. We recently identified through genome-wide analyses that Bmp2-Smad1 signal and its regulation by harmonized epigenomic alteration play an important role in Ras-induced senescence of mouse embryonic fibroblasts. We describe in this chapter the methods for analyses of epigenomic alteration and Smad1 targets on genome-wide scale. PMID:26520136

Cellularsenescence is characterized by growth arrest, enlarged and flattened cell morphology, the expression of senescence-associated β-galactosidase (SA-β-gal), and by activation of tumor suppressor networks. Insulin-like growth factor-I (IGF-I) plays a critical role in cellular growth, proliferation, tumorigenesis, and regulation of aging. In the present study, we show that IGF-I enhances cellularsenescence in mouse, rat, and human primary cells in the confluent state. IGF-I induced expression of a DNA damage marker, γH2AX, the increased levels of p53 and p21 proteins, and activated SA-β-gal. In the confluent state, an altered downstream signaling of IGF-I receptor was observed. Treatment with a reactive oxygen species (ROS) scavenger, N-acetylcystein (NAC) significantly suppressed induction of these markers, indicating that ROS are involved in the induction of cellularsenescence by IGF-I. In p53-null mouse embryonic fibroblasts, the IGF-I-induced augmentation of SA-β-gal and p21 was inhibited, demonstrating that p53 is required for cellularsenescence induced by IGF-I. Thus, these data reveal a novel pathway whereby IGF-I enhances cellularsenescence in the ROS and p53-dependent manner and may explain the underlying mechanisms of IGF-I involvement in tumorigenesis and in regulation of aging. PMID:22877754

Background Progressive neurological dysfunction is a key aspect of human aging. Because of underlying differences in the aging of mice and humans, useful mouse models have been difficult to obtain and study. We have used gene-expression analysis and polymorphism screening to study molecular senescence of the retina and hippocampus in two rare inbred mouse models of accelerated neurological senescence (SAMP8 and SAMP10) that closely mimic human neurological aging, and in a related normal strain (SAMR1) and an unrelated normal strain (C57BL/6J). Results The majority of age-related gene expression changes were strain-specific, with only a few common pathways found for normal and accelerated neurological aging. Polymorphism screening led to the identification of mutations that could have a direct impact on important disease processes, including a mutation in a fibroblast growth factor gene, Fgf1, and a mutation in and ectopic expression of the gene for the chemokine CCL19, which is involved in the inflammatory response. Conclusion We show that combining the study of inbred mouse strains with interesting traits and gene-expression profiling can lead to the discovery of genes important for complex phenotypes. Furthermore, full-genome polymorphism detection, sequencing and gene-expression profiling of inbred mouse strains with interesting phenotypic differences may provide unique insights into the molecular genetics of late-manifesting complex diseases. PMID:15960800

This study investigated the effect of isoflavone aglycone (IA) on the learning and memory performance of senescence-accelerated mice, and explored its neural protective mechanism. Results showed that SAM-P/8 senescence-accelerated mice treated with IA performed significantly better in the Y-maze cognitive test than the no treatment control (P less…

The senescence-accelerated mouse (SAM), consisting of 14 senescence-prone inbred strains (SAMP) and 4 senescence-resistant inbred strains (SAMR) has been under development since 1970 through the selective inbreeding of AKR/J strain mice donated by the Jackson laboratory in 1968, based on the data of the grading score of senescence, life span, and pathologic phenotypes. The characteristic feature of aging common to all SAMP and SAMR mice is acceleratedsenescence and normal aging, respectively. Furthermore, SAMP and SAMR strains manifest various pathobiological phenotypes which include such neurobiological phenotypes as deficits in learning and memory, emotional disorders, abnormal circadian rhythms, brain atrophy, hearing impairment, etc., and are often characteristic enough to differentiate the strains. Various efforts are currently being made using the SAM model to clarify the underlying mechanisms in acceleratedsenescence as well as the etiopathogenic mechanisms in age-associated pathobiologies. Genetic background and significance of SAM development are discussed. PMID:10537019

Persistent DNA damage is considered as a main cause of cellularsenescence induced by ionizing radiation. However, the molecular bases of the DNA damage and their contribution to cellularsenescence are not completely clear. In this study, we found that both heavy ions and X-rays induced senescence in human uveal melanoma 92–1 cells. By measuring senescence associated-β-galactosidase and cell proliferation, we identified that heavy ions were more effective at inducing senescence than X-rays. We observed less efficient repair when DNA damage was induced by heavy ions compared with X-rays and most of the irreparable damage was complex of single strand breaks and double strand breaks, while DNA damage induced by X-rays was mostly repaired in 24 hours and the remained damage was preferentially associated with telomeric DNA. Our results suggest that DNA damage induced by heavy ion is often complex and difficult to repair, thus presents as persistent DNA damage and pushes the cell into senescence. In contrast, persistent DNA damage induced by X-rays is preferentially associated with telomeric DNA and the telomere-favored persistent DNA damage contributes to X-rays induced cellularsenescence. These findings provide new insight into the understanding of high relative biological effectiveness of heavy ions relevant to cancer therapy and space radiation research. PMID:27187621

Persistent DNA damage is considered as a main cause of cellularsenescence induced by ionizing radiation. However, the molecular bases of the DNA damage and their contribution to cellularsenescence are not completely clear. In this study, we found that both heavy ions and X-rays induced senescence in human uveal melanoma 92-1 cells. By measuring senescence associated-β-galactosidase and cell proliferation, we identified that heavy ions were more effective at inducing senescence than X-rays. We observed less efficient repair when DNA damage was induced by heavy ions compared with X-rays and most of the irreparable damage was complex of single strand breaks and double strand breaks, while DNA damage induced by X-rays was mostly repaired in 24 hours and the remained damage was preferentially associated with telomeric DNA. Our results suggest that DNA damage induced by heavy ion is often complex and difficult to repair, thus presents as persistent DNA damage and pushes the cell into senescence. In contrast, persistent DNA damage induced by X-rays is preferentially associated with telomeric DNA and the telomere-favored persistent DNA damage contributes to X-rays induced cellularsenescence. These findings provide new insight into the understanding of high relative biological effectiveness of heavy ions relevant to cancer therapy and space radiation research. PMID:27187621

Cellularsenescence is an intrinsic defense mechanism to various cellular stresses: while still metabolically active, senescent cells stop dividing and enter a proliferation arrest. Here, we identify DPY30, a member of all mammalian histone H3K4 histone methyltransferases (HMTases), as a key regulator of the proliferation potential of human primary cells. Following depletion of DPY30, cells show a severe proliferation defect and display a senescent phenotype, including a flattened and enlarged morphology, elevated level of reactive oxygen species (ROS), increased SA-β-galactosidase activity, and formation of senescence-associated heterochromatin foci (SAHFs). While DPY30 depletion leads to a reduced level of H3K4me3-marked active chromatin, we observed a concomitant activation of CDK inhibitors, including p16INK4a, independent of H3K4me3. ChIP experiments show that key regulators of cell-cycle progression, including ID proteins, are under direct control of DPY30. Because ID proteins are negative regulators of the transcription factors ETS1/2, depletion of DPY30 leads to the transcriptional activation of p16INK4a by ETS1/2 and thus to a senescent-like phenotype. Ectoptic re-introduction of ID protein expression can partially rescue the senescence-like phenotype induced by DPY30 depletion. Thus, our data indicate that DPY30 controls proliferation by regulating ID proteins expression, which in turn lead to senescence bypass. PMID:23872946

Mitochondria are dynamic organelles, which couple the various cellular processes that regulate metabolism, cell proliferation and survival. Environmental stress can cause mitochondrial dysfunction and dynamic changes including reduced mitochondrial biogenesis, oxidative phosphorylation and ATP production, as well as mitophagy impairment, which leads to increased ROS, inflammatory responses and cellularsenescence. Oxidative stress, inflammation and cellularsenescence all have important roles in the pathogenesis of chronic lung diseases, such as chronic obstructive pulmonary disease, pulmonary fibrosis and bronchopulmonary dysplasia. In this review, we discuss the current state on how mitochondrial dysfunction affects inflammatory responses and cellularsenescence, the mechanisms of mitochondrial dysfunction underlying the pathogenesis of chronic lung diseases and the potential of mitochondrial transfer and replacement as treatments for these diseases. PMID:27189175

Described is an in vitro model of premature senescence in pulmonary adenocarcinoma A549 cells induced by persistent DNA replication stress in response to treatment with the DNA damaging drug mitoxantrone (Mxt). The degree of cellularsenescence, based on characteristic changes in cell morphology, is measured by laser scanning cytometry. Specifically, the flattening of cells grown on slides (considered the hallmark of cellularsenescence) is measured as the decline in local intensity of DNA-associated DAPI fluorescence (represented by maximal pixels). This change is paralleled by an increase in nuclear area. Thus, the ratio of mean intensity of maximal pixels to nuclear area provides a very sensitive morphometric biomarker for the degree of senescence. This analysis is combined with immunocytochemical detection of senescence markers, such as overexpression of cyclin kinase inhibitors (e.g., p21WAF1) and phosphorylation of ribosomal protein S6 (rpS6), a key marker associated with aging/senescence that is detected using a phospho-specific antibody. These biomarker indices are presented in quantitative terms defined as a senescence index (SI), which is the fraction of the marker in test cultures relative to the same marker in exponentially growing control cultures. This system can be used to evaluate the anti-aging potential of test agents by assessing attenuation of maximal senescence. As an example, the inclusion of berberine, a natural alkaloid with reported anti-aging properties and a long history of use in traditional Chinese medicine, is shown to markedly attenuate the Mxt-induced SI and phosphorylation of rpS6. The multivariate analysis of senescence markers by laser scanning cytometry offers a promising tool to explore the potential anti-aging properties of a variety agents. PMID:24984966

Although pituitary adenomas represent 25% of intracranial tumors, they are usually benign, with the mechanisms by which these tumors usually avoid an invasive profile and metastatic growth development still remaining unclear. In this context, cellularsenescence might constitute a plausible explanation for the benign nature of pituitary adenomas. In this study, we investigated the emergence of cellularsenescence as a growth control mechanism during the progression of estrogen-induced pituitary tumors. The quantification of Ki67-immunopositive cells in the pituitaries of estrogenized male rats after 10, 20, 40, and 60 days revealed that the mitogenic potential rate was not sustained for the whole period analyzed and successively decreased after 10 days of estrogen exposure. In addition, the expression of cellularsenescence features, such as the progressive rise in the enzymatic senescence-associated b-galactosidase (SA-b-gal) activity, IL6, IL1b, and TGFb expression, was observed throughout pituitary tumor development. Furthermore, tumoral pituitary cells also displayed nuclear pATM expression, indicating activated DNA damage signaling, with a significant increase in p21 expression also being detected. The associations among DNA damage signaling activation, SA-b-gal expression, and p21 may provide a reliable combination of senescence-associated markers for in vivo pituitary senescence detection. These results suggest a role for this cellular process in the regulation of pituitary cell growth. Thus, cellularsenescence should be conceived as a contributing component to the benign nature of pituitary adenomas, thereby influencing the capability of the pituitary gland to avoid unregulated cell proliferation. PMID:25792544

Chronic, low grade, sterile inflammation frequently accompanies aging and age-related diseases. Cellularsenescence is associated with the production of proinflammatory chemokines, cytokines, and extracellular matrix (ECM) remodeling proteases, which comprise the senescence-associated secretory phenotype (SASP). We found a higher burden of senescent cells in adipose tissue with aging. Senescent human primary preadipocytes as well as human umbilical vein endothelial cells (HUVECs) developed a SASP that could be suppressed by targeting the JAK pathway using RNAi or JAK inhibitors. Conditioned medium (CM) from senescent human preadipocytes induced macrophage migration in vitro and inflammation in healthy adipose tissue and preadipocytes. When the senescent cells from which CM was derived had been treated with JAK inhibitors, the resulting CM was much less proinflammatory. The administration of JAK inhibitor to aged mice for 10 wk alleviated both adipose tissue and systemic inflammation and enhanced physical function. Our findings are consistent with a possible contribution of senescent cells and the SASP to age-related inflammation and frailty. We speculate that SASP inhibition by JAK inhibitors may contribute to alleviating frailty. Targeting the JAK pathway holds promise for treating age-related dysfunction. PMID:26578790

Cellularsenescence, a state of essentially irreversible proliferation arrest, serves as a potent tumour suppressor mechanism. However, accumulation of senescent cells with chronological age is likely to contribute to loss of tissue and organ function and organismal aging. A crucial biochemical modulator of aging is mTOR; here, we have addressed the question of whether acute mTORC inhibition in near-senescent cells can modify phenotypes of senescence. We show that acute short term treatment of human skin fibroblasts with low dose ATP mimetic pan-mTORC inhibitor AZD8055 leads to reversal of many phenotypes that develop as cells near replicative senescence, including reduction in cell size and granularity, loss of SA-β-gal staining and reacquisition of fibroblastic spindle morphology. AZD8055 treatment also induced rearrangement of the actin cytoskeleton, providing a possible mechanism of action for the observed rejuvenation. Importantly, short-term drug exposure had no detrimental effects on cell proliferation control across the life-course of the fibroblasts. Our findings suggest that combined inhibition of both mTORC1 and mTORC2 may provide a promising strategy to reverse the development of senescence-associated features in near-senescent cells. PMID:26851731

Cellularsenescence, a state of essentially irreversible proliferation arrest, serves as a potent tumour suppressor mechanism. However, accumulation of senescent cells with chronological age is likely to contribute to loss of tissue and organ function and organismal aging. A crucial biochemical modulator of aging is mTOR; here, we have addressed the question of whether acute mTORC inhibition in near-senescent cells can modify phenotypes of senescence. We show that acute short term treatment of human skin fibroblasts with low dose ATP mimetic pan-mTORC inhibitor AZD8055 leads to reversal of many phenotypes that develop as cells near replicative senescence, including reduction in cell size and granularity, loss of SA-β-gal staining and reacquisition of fibroblastic spindle morphology. AZD8055 treatment also induced rearrangement of the actin cytoskeleton, providing a possible mechanism of action for the observed rejuvenation. Importantly, short-term drug exposure had no detrimental effects on cell proliferation control across the life-course of the fibroblasts. Our findings suggest that combined inhibition of both mTORC1 and mTORC2 may provide a promising strategy to reverse the development of senescence-associated features in near-senescent cells. PMID:26851731

Cellularsenescence can be prematurely induced by oxidative stress involved in aging. In this work, we were searching for novel intermediaries in oxidative stress-induced senescence, focusing our interest on integrin-linked kinase (ILK), a scaffold protein at cell-extracellular matrix (ECM) adhesion sites, and on the Klotho gene. Cultured renal cells were treated with glucose oxidase (GOx) for long time periods. GOx induced senescence, increasing senescence associated β-galactosidase activity and the expression of p16. In parallel, GOx increased ILK protein expression and activity. Ectopic overexpression of ILK in cells increased p16 expression, even in the absence of GOx, whereas downregulation of ILK inhibited the increase in p16 due to oxidative stress. Additionally, GOx reduced Klotho gene expression and cells overexpressing Klotho protein did not undergo senescence after GOx addition. We demonstrated a direct link between ILK and Klotho since silencing ILK expression in cells and mice increases Klotho expression and reduces p53 and p16 expression in renal cortex. In conclusion, oxidative stress induces cellularsenescence in kidney cells by increasing ILK protein expression and activity, which in turn reduces Klotho expression. We hereby present ILK as a novel downregulator of Klotho gene expression. PMID:26583057

Cellularsenescence can be prematurely induced by oxidative stress involved in aging. In this work, we were searching for novel intermediaries in oxidative stress-induced senescence, focusing our interest on integrin-linked kinase (ILK), a scaffold protein at cell-extracellular matrix (ECM) adhesion sites, and on the Klotho gene. Cultured renal cells were treated with glucose oxidase (GOx) for long time periods. GOx induced senescence, increasing senescence associated β-galactosidase activity and the expression of p16. In parallel, GOx increased ILK protein expression and activity. Ectopic overexpression of ILK in cells increased p16 expression, even in the absence of GOx, whereas downregulation of ILK inhibited the increase in p16 due to oxidative stress. Additionally, GOx reduced Klotho gene expression and cells overexpressing Klotho protein did not undergo senescence after GOx addition. We demonstrated a direct link between ILK and Klotho since silencing ILK expression in cells and mice increases Klotho expression and reduces p53 and p16 expression in renal cortex. In conclusion, oxidative stress induces cellularsenescence in kidney cells by increasing ILK protein expression and activity, which in turn reduces Klotho expression. We hereby present ILK as a novel downregulator of Klotho gene expression. PMID:26583057

Cellularsenescence has evolved from an in-vitro model system to study aging in vitro to a multifaceted phenomenon of in-vivo importance as senescent cells in vivo have been identified and their removal delays the onset of age-associated diseases in a mouse model system. From the large emerging class of non-coding RNAs, miRNAs have only recently been functionally implied in the regulatory networks that are modified during the aging process. Here we summarize examples of similarities between the differential expression of miRNAs during senescence and age-associated diseases and suggest that these similarities might emphasize the importance of senescence for the pathogenesis of age-associated diseases. Understanding such a connection on the level of miRNAs might offer valuable opportunities for designing novel diagnostic and therapeutic strategies. PMID:24472232

A novel target of NESH-SH3 (TARSH) was identified as a cellularsenescence related gene in mouse embryonic fibroblasts (MEFs) replicative senescence, the expression of which has been suppressed in primary clinical lung cancer specimens. However, the molecular mechanism underlying the regulation of TARSH involved in pulmonary tumorigenesis remains unclear. Here we demonstrate that the reduction of TARSH gene expression by short hairpin RNA (shRNA) system robustly inhibited the MEFs proliferation with increase in senescence-associated {beta}-galactosidase (SA-{beta}-gal) activity. Using p53{sup -/-} MEFs, we further suggest that this growth arrest by loss of TARSH is evoked by p53-dependent p21{sup Cip1} accumulation. Moreover, we also reveal that TARSH reduction induces multicentrosome in MEFs, which is linked in chromosome instability and tumor development. These results suggest that TARSH plays an important role in proliferation of replicative senescence and may serve as a trigger of tumor development.

Cellularsenescence is an initial barrier for carcinogenesis. However, the signaling mechanisms that trigger cellularsenescence are incompletely understood, particularly in vivo. Here we identify Wnt7a as a novel upstream inducer of cellularsenescence. In two different mouse strains (C57Bl/6J and FVB/NJ), we show that the loss of Wnt7a is a major contributing factor for increased lung tumorigenesis owing to reduced cellularsenescence, and not reduced apoptosis, or autophagy. Wnt7a-null mice under de novo conditions and in both the strains display E-cadherin-to-N-cadherin switch, reduced expression of cellularsenescence markers and reduced expression of senescence-associated secretory phenotype, indicating a genetic predisposition of these mice to increased carcinogen-induced lung tumorigenesis. Interestingly, Wnt7a induced an alternate senescence pathway, which was independent of β-catenin, and distinct from that of classical oncogene-induced senescence mediated by the well-known p16INK4a and p19ARF pathways. Mechanistically, Wnt7a induced cellularsenescence via inactivation of S-phase kinase-associated protein 2, an important alternate regulator of cellularsenescence. Additionally, we identified Iloprost, a prostacyclin analog, which initiates downstream signaling cascades similar to that of Wnt7a, as a novel inducer of cellularsenescence, presenting potential future clinical translational strategies. Thus pro-senescence therapies using either Wnt7a or its mimic, Iloprost, might represent a new class of therapeutic treatments for lung cancer. PMID:25728679

Senescence, a terminal cell proliferation arrest that is caused by a variety of cellular stresses such as telomere erosion, DNA damage and oncogenic signaling, is classically considered a tumor defense barrier. However, the mechanism by which cancer cells overcome senescence is undetermined. In this study, the gene expression array data of esophageal squamous cell carcinoma (ESCC) was compared with paired normal tissues and showed that a cohort of genes, including proteinases, chemokines and inflammation factors, are upregulated in ESCC, which exhibits the senescence-associated secretory phenotype. In addition, reverse transcription-quantitative polymerase chain reaction was used to demonstrate that gender determining region Y-box 4 (SOX4) is upregulated in ESCC, and that its expression is inversely correlated with senescence markers. In addition, the knockdown of SOX4 expression by short hairpin RNA decreases ESCC cell proliferation and enhances doxorubicin-induced cell senescence. These results reveal the presence of a senescent microenvironment in ESCC, and suggest an important antisenescence role of SOX4 in ESCC progression. PMID:27446439

Although mitochondrial stress is a key determinant of cellular homeostasis, the intracellular mechanisms by which this stress is communicated to the nucleus and its impact on cell fate decisions are not well defined. In this study, we report that activation of mTORC1 signaling triggered by mitochondrial-generated reactive oxygen species (ROS) results in activation of the senescence program. We show that exposure of human fibroblasts to nucleoside analogs commonly used in antiretroviral therapies, and known to induce mitochondrial dysfunction, increases mitochondrial ROS and leads to a rise in intracellular ROS concomitant with activation of mTORC1. In this setting, it appears that mTORC1 activates senescence through HDM2 phosphorylation, facilitating a p53-mediated response. Inhibition of mTORC1 by rapamycin decreases HDM2 phosphorylation and blocks activation of the senescence program in human cells. In addition, decreasing mitochondrial ROS directly blocks mTORC1 signaling and prevents the onset of senescence. Consistent with these results, both total and mitochondrial-specific ROS increased in cells undergoing replicative senescence along with ribosomal p70 phosphorylation. The results reveal a novel link between mitochondrial dysfunction, mTORC1 signaling, and the senescence program. PMID:27016071

The process of cellularsenescence generates a repressive chromatin environment, however, the role of histone variants and histone proteolytic cleavage in senescence remains unclear. Using models of oncogene-induced and replicative senescence, here we report novel histone H3 tail cleavage events mediated by the protease Cathepsin L. We find that cleaved forms of H3 are nucleosomal and the histone variant H3.3 is the preferred cleaved form of H3. Ectopic expression of H3.3 and its cleavage product (H3.3cs1), which lacks the first twenty-one amino acids of the H3 tail, is sufficient to induce senescence. Further, H3.3cs1 chromatin incorporation is mediated by the HUCA histone chaperone complex. Genome-wide transcriptional profiling revealed that H3.3cs1 facilitates transcriptional silencing of cell cycle regulators including RB/E2F target genes, likely via the permanent removal of H3K4me3. Collectively, our study identifies histone H3.3 and its proteolytically processed forms as key regulators of cellularsenescence. PMID:25394905

We have mapped a cellularsenescence gene, SEN16, within a genetic distance of 3 - 7 cM, at 16q24.3. Microcell mediated transfer of a normal human chromosome 16, 16q22-qter or 16q23-qter restored cellularsenescence in four immortal cell lines, derived from human and rat mammary tumors. The resumption of indefinite cell proliferation, concordant with the segregation of the donor chromosome, confirmed the presence of a senescence gene at 16q23-qter. While microcell hybrids were maintained in selection medium to retain the donor chromosome, sporadic immortal revertant clones arose among senescent cells. Reversion to immortal growth could occur due to inactivation of the senescence gene either by a mutation or a deletion. The analysis for chromosome 16 specific DNA markers, in revertant clones of senescent microcell hybrids, revealed a consensus deletion, spanning a genetic interval of approximately 3 - 7 cM at 16q24.3. PMID:10490846

Highlights: Black-Right-Pointing-Pointer Phenylbutyric acid induces cellularsenescence. Black-Right-Pointing-Pointer Phenylbutyric acid activates Akt kinase. Black-Right-Pointing-Pointer The knockdown of PERK also can induce cellularsenescence. Black-Right-Pointing-Pointer Akt/p21{sup WAF1} pathway activates in PERK knockdown induced cellularsenescence. -- Abstract: It has been well known that three sentinel proteins - PERK, ATF6 and IRE1 - initiate the unfolded protein response (UPR) in the presence of misfolded or unfolded proteins in the ER. Recent studies have demonstrated that upregulation of UPR in cancer cells is required to survive and proliferate. Here, we showed that long exposure to 4-phenylbutyric acid (PBA), a chemical chaperone that can reduce retention of unfolded and misfolded proteins in ER, induced cellularsenescence in cancer cells such as MCF7 and HT1080. In addition, we found that treatment with PBA activates Akt, which results in p21{sup WAF1} induction. Interestingly, the depletion of PERK but not ATF6 and IRE1 also induces cellularsenescence, which was rescued by additional depletion of Akt. This suggests that Akt pathway is downstream of PERK in PBA induced cellularsenescence. Taken together, these results show that PBA induces cellularsenescence via activation of the Akt/p21{sup WAF1} pathway by PERK inhibition.

High-affinity sodium-dependent dicarboxylate cotransporter 3 (NaDC3) is a key metabolism-regulating membrane protein responsible for transport of Krebs cycle intermediates. NaDC3 is upregulated as organs age, but knowledge regarding the underlying mechanisms by which NaDC3 modulates mammalian aging is limited. In this study, we showed that NaDC3 overexpression acceleratedcellularsenescence in young human diploid cells (MRC-5 and WI-38) and primary renal tubular cells, leading to cell cycle arrest in G1 phase and increased expression of senescent biomarkers, senescence-associated β-galactosidase and p16. Intracellular levels of reactive oxygen species, 8-hydroxy-2'-deoxyguanosine, malondialdehyde, and carbonyl were significantly enhanced, and activities of respiratory complexes I and III and ATP level were significantly decreased in NaDC3-infected cells. Stressful premature senescent phenotypes induced by NaDC3 were markedly ameliorated via treatment with the antioxidants Tiron and Tempol. High expression of NaDC3 caused a prominent increase in intracellular levels of Krebs cycle intermediates and NADH. Exogenous NADH and NAD(+) may aggravate and attenuate the aging phenotypes induced by NaDC3, respectively. These results suggest that NaDC3 can induce premature cellularsenescence by promoting the transport of Krebs cycle intermediates, increasing generation of NADH and reactive oxygen species and leading to oxidative damage. Our results clarify the aging signaling pathway regulated by NaDC3. PMID:25384549

Reactive oxygen species (ROS) can cause severe damage to DNA, proteins and lipids in normal cells, contributing to carcinogenesis and various pathological conditions. While cellularsenescence arrests the early phase of cell cycle without any detectable telomere loss or dysfunction. ROS is reported to contribute to induction of cellularsenescence, as evidence by its premature onset upon treatment with antioxidants or inhibitors of cellular oxidant scavengers. Although cellularsenescence is known to be implicated in tumor suppression, it remains unknown whether ROS initially contributed to be cellularsenescence in normal human epidermal keratinocytes (NHEK) and their malignant counterparts. To clarify whether ROS induce cellularsenescence in NHEKs, we examined the effect of hydrogen peroxide (H2O2) on the expression of cellularsenescence-associated molecules in NHEKs, compared to in squamous carcinoma cells (SCCs). Hydrogen peroxide increased the number of cells positive in senescence associated-β-galactosidase (SA-β-Gal) activity in NHEKs, but not SCCs. The expression of cyclin-dependent kinase (CDK) inhibitors, especially p16(INK4a) was upregulated in NHEKs treated with H2O2. Interestingly, H2O2 suppressed the methylation of p16(INK4a), promoter region in NHEKs, but not in SCCs. Hydrogen peroxide also suppressed the expression of phosphorylated Rb and CDK4, resulting in arrest in G0/G1 phase in NHEKs, but not SCCs. Our results indicate that the ROS-induced cellularsenescence in NHEKs was caused by the upregulation p16(INK4a) through demethylation in its promoter region, which is not detected in SCCs, suggesting that ROS-induced cellularsenescence contributes to tumor suppression of NHEKs. PMID:25181340

Cellularsenescence, the stable cell cycle arrest elicited by various forms of stress, is an important facet of tumor suppression. Although much is known about the key players in the implementation of senescence, including the pRb and p53 axes and the cyclin dependent kinase inhibitors p16INK4a and p21CIP1, many details remain unresolved. In studying conditional senescence in human fibroblasts that express a temperature sensitive SV40 large T-antigen (T-Ag), we uncovered an unexpected role for CDK4. At the permissive temperature, where pRb and p53 are functionally compromised by T-Ag, cyclin D-CDK4 complexes are disrupted by the high p16INK4a levels and reduced expression of p21CIP1. In cells arrested at the non-permissive temperature, p21CIP1 promotes reassembly of cyclin D-CDK4 yet pRb is in a hypo-phosphorylated state, consistent with cell cycle arrest. In exploring whether the reassembled cyclin D-CDK4-p21 complexes are functional, we found that shRNA-mediated knockdown or chemical inhibition of CDK4 prevented the increase in cell size associated with the senescent phenotype by allowing the cells to arrest in G1 rather than G2/M. The data point to a role for CDK4 kinase activity in a G2 checkpoint that contributes to senescence. PMID:25695870

Taurine (2-aminoethanesulfonic acid) is found in milimolar concentrations in mammalian tissues. One of its main functions is osmoregulation; however, it also exhibits cytoprotective activity by diminishing injury caused by stress and disease. Taurine depletion is associated with several defects, many of which are found in the aging animal, suggesting that taurine might exert anti-aging actions. Therefore, in the present study, we examined the hypothesis that taurine depletion accelerates aging by reducing longevity and accelerating aging-associated tissue damage. Tissue taurine depletion in taurine transporter knockout (TauTKO) mouse was found to shorten lifespan and accelerate skeletal muscle histological and functional defects, including an increase in central nuclei containing myotubes, a reduction in mitochondrial complex 1 activity and an induction in an aging biomarker, Cyclin-dependent kinase 4 inhibitor A (p16INK4a). Tissue taurine depletion also enhances unfolded protein response (UPR), which may be associated with an improvement in protein folding by taurine. Our data reveal that tissue taurine depletion affects longevity and cellularsenescence; an effect possibly linked to a disturbance in protein folding. PMID:25229346

Microgravity has a unique effect on biological organisms. Organs exposed to microgravity display cellularsenescence, a change that resembles the aging process. To directly investigate the influence of simulated microgravity on neuronal original rat PC12 cells, we used a rotary cell culture system that simulates the microgravity environment on the earth. We found that simulated microgravity induced partial G1 phase arrest, upregulated senescence-associated beta-galactosidase (SA-beta-gal) activity, and activated both p53 and p16 protein pathways linked to cell senescence. The amount of reactive oxygen species (ROS) was also increased. The activity of intracellular antioxidant enzymes, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), was all significantly increased at 12h after the microgravity onset, yet decreased at 96h. Furthermore, concomitant block of ROS by the antioxidant N-acetylcysteine significantly inhibited the microgravity-induced upregulation of SA-beta-gal activity. These results suggest that exposure to simulated microgravity induces cellularsenescence in PC12 cells via an increased oxidant stress. PMID:19616052

We utilized high-density Affymetrix oligonucleotide arrays to investigate gene expression in the olfactory mucosae of near age-matched aging senescence-accelerated mice (SAM). The senescence-prone (SAMP) strain has a significantly shorter lifespan than does the senescence-resistant (SAMR) strain. To analyze our data, we applied biostatistical methods that included a correlation analysis to evaluate sources of methodologic and biological variability; a two-sided t-test to identify a subpopulation of Present genes with a biologically relevant P-value <0.05; and a false discovery rate (FDR) analysis adjusted to a stringent 5% level that yielded 127 genes with a P-value of <0.001 that were differentially regulated in near age-matched SAMPs (SAMP-Os; 13.75 months) compared to SAMRs (SAMR-Os, 12.5 months). Volcano plots related the variability in the mean hybridization signals as determined by the two-sided t-test to fold changes in gene expression. The genes were categorized into the six functional groups used previously in gene profiling experiments to identify candidate genes that may be relevant for senescence at the genomic and cellular levels in the aging mouse brain (Lee et al. [2000] Nat Genet 25:294-297) and in the olfactory mucosa (Getchell et al. [2003] Ageing Res Rev 2:211-243), which serves several functions that include chemosensory detection, immune barrier function, xenobiotic metabolism, and neurogenesis. Because SAMR-Os and SAMP-Os have substantially different median lifespans, we related the rate constant alpha in the Gompertz equation on aging to intrinsic as opposed to environmental mechanisms of senescence based on our analysis of genes modulated during aging in the olfactory mucosa. PMID:15248299

The possibility to target cellularsenescence with natural bioactive substances open interesting therapeutic perspective in cancer and aging. Engaging senescence response is suggested as a key component for therapeutic intervention in the eradication of cancer. At the same time, delaying senescence or even promote death of accumulating apoptosis-resistant senescent cells is proposed as a strategy to prevent age related diseases. Although these two desired outcome present an intrinsic dichotomy, there are examples of promising natural compounds that appear to satisfy all the requirements to develop senescence- targeted health promoting nutraceuticals. Tocotrienols (T3s) and quercetin (QUE), albeit belonging to different phytochemical classes, display similar and promising effects "in vitro" when tested in normal and cancer cells. Both compounds have been shown to induce senescence and promote apoptosis in a multitude of cancer lines. Conversely, they display senescence delaying activity in primary cells and rejuvenating effects in senescent cells. More recently, QUE has been shown to display senolytic effects in some primary senescent cells, likely as a consequence of its inhibitory effects on specific anti-apoptotic genes (i.e. PI3K and other kinases). Senolytic activity has not been tested for T3s but part of metabolic and apoptotic pathways affected by these compounds in cancer cells overlap with those of QUE. This suggests that the rejuvenating effects of T3s and QUE on pre-senescent and senescent primary cells might be the net results of a senolytic activity on senescent cells and a selective survival of a sub-population of non-senescent cells in the culture. The meaning of this hypothesis in the context of adjuvant therapy of cancer and preventive anti-aging strategies with QUE or T3s is discussed. PMID:26343116

DNA damage response is crucially involved in cellularsenescence. We have previously shown that excess thymidine, which stalls DNA replication forks, induces cellularsenescence in human cells, and ERK1/2 play a key role in the induction of it. In this study, we found that Chk1 and ERK1/2 were activated to promote cell survival upon addition of excess thymidine. Knockdown of ERK1/2 activated Chk1, and conversely, knockdown of Chk1 activated ERK1/2, which observations suggested a mechanism for compensatory activation of Chk1 and ERK1/2 in the absence of ERK1/2 and Chk1, respectively. We also found that Chk1 functioned mainly at the onset of cellularsenescence, and on the other hand, ERK1/2 functioned for a more extended period to induce cellularsenescence. Our findings suggested that Chk1 and ERK1/2 were activated to promote cell survival upon addition of excess thymidine, but prolonged activation of ERK1/2 led to cellularsenescence. This implies a pleiotropic effect of ERK1/2 in cellularsenescence induced by excess thymidine. PMID:27443255

The Senescence-Accelerated Mouse (SAM) strains constitute a murine model of acceleratedsenescence originating from the ancestral AKR/J strains and consist of nine senescence-prone (SAMP) strains and four senescence-resistant (SAMR) strains. The chromosomes (Chrs) of the SAM strains were typed with 581 microsatellite markers amplified by PCR, and the fundamental genetic information of the SAM strains was obtained. One-third of the examined markers displayed polymorphism among the strains, and only two alleles were detected in almost all loci among the SAM and AKR/J strains. However, in 12 loci (5.6% of total 215 polymorphic markers), the third allele was detected among the SAM strains. The genetic typing and developmental history suggested that the SAM strains were related inbred strains developed by the accidental crossing between the AKR/J strain and other unknown strain(s). Comparison of the distribution of the loci in the SAMP and the SAMR series revealed notable differences in the four regions on Chrs 4, 14, 16, and 17. This indicated that some of these chromosomal sites might contain the genes responsible for acceleratedsenescence in the SAMP series. PMID:10051317

Human respiratory syncytial virus (HRSV) accounts for the majority of lower respiratory tract infections during infancy and childhood and is associated with significant morbidity and mortality. HRSV provokes a proliferation arrest and characteristic syncytia in cellular systems such as immortalized epithelial cells. We show here that HRSV induces the expression of DNA damage markers and proliferation arrest such as P-TP53, P-ATM, CDKN1A and γH2AFX in cultured cells secondary to the production of mitochondrial reactive oxygen species (ROS). The DNA damage foci contained γH2AFX and TP53BP1, indicative of double-strand breaks (DSBs) and could be reversed by antioxidant treatments such as N-Acetylcysteine (NAC) or reduced glutathione ethyl ester (GSHee). The damage observed is associated with the accumulation of senescent cells, displaying a canonical senescent phenotype in both mononuclear cells and syncytia. In addition, we show signs of DNA damage and aging such as γH2AFX and CDKN2A expression in the respiratory epithelia of infected mice long after viral clearance. Altogether, these results show that HRSV triggers a DNA damage-mediated cellularsenescence program probably mediated by oxidative stress. The results also suggest that this program might contribute to the physiopathology of the infection, tissue remodeling and aging, and might be associated to long-term consequences of HRSV infections. PMID:26809688

Autologous c-kit+ cardiac progenitor cells (CPCs) are currently used in the clinic to treat heart disease. CPC-based regeneration may be further augmented by better understanding molecular mechanisms of endogenous cardiac repair and enhancement of pro-survival signaling pathways that antagonize senescence while also increasing differentiation. The prolyl isomerase Pin1 regulates multiple signaling cascades by modulating protein folding and thereby activity and stability of phosphoproteins. In this study, we examine the heretofore unexplored role of Pin1 in CPCs. Pin1 is expressed in CPCs in vitro and in vivo and is associated with increased proliferation. Pin1 is required for cell cycle progression and loss of Pin1 causes cell cycle arrest in the G1 phase in CPCs, concomitantly associated with decreased expression of Cyclins D and B and increased expression of cell cycle inhibitors p53 and retinoblastoma (Rb). Pin1 deletion increases cellularsenescence but not differentiation or cell death of CPCs. Pin1 is required for endogenous CPC response as Pin1 knock-out mice have a reduced number of proliferating CPCs after ischemic challenge. Pin1 overexpression also impairs proliferation and causes G2/M phase cell cycle arrest with concurrent down-regulation of Cyclin B, p53, and Rb. Additionally, Pin1 overexpression inhibits replicative senescence, increases differentiation, and inhibits cell death of CPCs, indicating that cell cycle arrest caused by Pin1 overexpression is a consequence of differentiation and not senescence or cell death. In conclusion, Pin1 has pleiotropic roles in CPCs and may be a molecular target to promote survival, enhance repair, improve differentiation, and antagonize senescence. PMID:24375406

Mammalian cells, when treated with sub-lethal doses of genotoxic stresses, slow down DNA synthesis but continue protein synthesis. Thus, these cells show an accumulation of proteins and undergo unbalanced growth. In the previous studies, we have shown that HeLa cells treated with excess thymidine or camptothecin undergo unbalanced growth, and prolonged unbalanced growth causes induction of cellularsenescence, which is suppressed by restriction of protein synthesis or inhibition of ERK-signaling. In this study, we found that restriction of protein synthesis, inhibition of ERK-signaling, and elimination of reactive oxygen species showed a combinatorial effect on suppression of cellularsenescence induced by excess thymidine or camptothecin. Of these, restriction of protein synthesis most effectively suppressed cellularsenescence. Importantly, a similar combinatorial effect was observed in replicative senescence in normal human diploid fibroblasts. Our findings suggested that various stresses were cumulatively involved in cellularsenescence, and suppression of cellularsenescence was improved by combining the treatments that reduce the stresses. PMID:27339653

During aging, experimental studies have revealed various cellular changes, principal among which is myocyte hypertrophy, which compensates for the loss of myocytes and is associated with fibrosis. The expression of alpha-myosin heavy chain is replaced by that of the isogene beta-myosin, which leads to decreased myosin adenosine triphosphatase (ATPase) activity. In consequence, contraction is slower and more energetically economical. The Ca(2+)-ATPase of the sarcoplasmic reticulum and Na+/Ca2+ exchange activity are decreased, which probably explains the reduced velocity of relaxation. Membrane receptors are also modified, since the density of both the total beta-adrenergic and muscarinic receptors is decreased. The senescent heart is able to hypertrophy in response to overload and to adapt to the new requirements. Similar alterations are observed both in the senescent heart and in the overloaded heart, in clinical as well as in experimental studies; however, differences do exist, especially in terms of fibrosis and arrhythmias. PMID:7495213

Senescence of vascular endothelial cells leads to endothelial dysfunction and contributes to the progression of atherosclerosis. Liver X receptors (LXRs) are nuclear receptors whose activation protects against atherosclerosis by transcriptional regulation of genes important in promoting cholesterol efflux and inhibiting inflammation. Here we found that LXR activation with specific ligands reduced the increase in senescence-associated (SA) β-gal activity, a senescence marker, and reversed the decrease in telomerase activity, a replicative senescence marker, in human endothelial cells under high glucose. This effect of LXR activation was associated with reduced reactive oxygen species and increased endothelial NO synthase activity. A series of experiments that used siRNAs indicated that LXRβ mediates the prevention of endothelial cellularsenescence, and that sterol regulatory element binding protein-1, which was up-regulated as a direct LXRβ target gene, may act as a brake of endothelial cellularsenescence. Although oral administration of the LXR ligand led to severe fatty liver in diabetic rats, concomitant therapy with metformin avoided the development of hepatic steatosis. However, the preventive effect of the LXR ligand on SA β-gal–stained cells in diabetic aortic endothelium was preserved even if metformin was coadministered. Taken together, our studies demonstrate that an additional mechanism, such as the regulation of endothelial cellularsenescence, is related to the antiatherogenic properties of LXRs, and concomitant treatment with metformin may provide a clinically useful therapeutic strategy to alleviate an LXR activation-mediated adverse effects on liver triglyceride metabolism. PMID:24398515

Oxidative stress and persistent DNA damage response contribute to cellularsenescence, a degeneration process critically involving ataxia telangiectasia-mutated (ATM) and p53. Selenoprotein H (SelH), a nuclear selenoprotein, is proposed to carry redox and transactivation domains. To determine the role of SelH in genome maintenance, shRNA knockdown was employed in human normal and immortalized cell lines. SelH shRNA MRC-5 diploid fibroblasts under ambient O2 displayed a distinct profile of senescence including β-galactosidase expression, autofluorescence, growth inhibition, and ATM pathway activation. Such senescence phenotypes were alleviated in the presence of ATM kinase inhibitors, by p53 shRNA knockdown, or by maintaining the cells under 3% O2. During the course of 5-day recovery, the induction of phospho-ATM on Ser-1981 and γH2AX by H2O2 treatment (20 μm) subsided in scrambled shRNA but exacerbated in SelH shRNA MRC-5 cells. Results from clonogenic assays demonstrated hypersensitivity of SelH shRNA HeLa cells to paraquat and H2O2, but not to hydroxyurea, neocarzinostatin, or camptothecin. While SelH mRNA expression was induced by H2O2 treatment, SelH-GFP did not mobilize to sites of oxidative DNA damage. The glutathione level was lower in SelH shRNA than scrambled shRNA HeLa cells, and the H2O2-induced cell death was rescued in the presence of N-acetylcysteine, a glutathione precursor. Altogether, SelH protects against cellularsenescence to oxidative stress through a genome maintenance pathway involving ATM and p53. PMID:25336634

Oxidative stress and persistent DNA damage response contribute to cellularsenescence, a degeneration process critically involving ataxia telangiectasia-mutated (ATM) and p53. Selenoprotein H (SelH), a nuclear selenoprotein, is proposed to carry redox and transactivation domains. To determine the role of SelH in genome maintenance, shRNA knockdown was employed in human normal and immortalized cell lines. SelH shRNA MRC-5 diploid fibroblasts under ambient O2 displayed a distinct profile of senescence including β-galactosidase expression, autofluorescence, growth inhibition, and ATM pathway activation. Such senescence phenotypes were alleviated in the presence of ATM kinase inhibitors, by p53 shRNA knockdown, or by maintaining the cells under 3% O2. During the course of 5-day recovery, the induction of phospho-ATM on Ser-1981 and γH2AX by H2O2 treatment (20 μm) subsided in scrambled shRNA but exacerbated in SelH shRNA MRC-5 cells. Results from clonogenic assays demonstrated hypersensitivity of SelH shRNA HeLa cells to paraquat and H2O2, but not to hydroxyurea, neocarzinostatin, or camptothecin. While SelH mRNA expression was induced by H2O2 treatment, SelH-GFP did not mobilize to sites of oxidative DNA damage. The glutathione level was lower in SelH shRNA than scrambled shRNA HeLa cells, and the H2O2-induced cell death was rescued in the presence of N-acetylcysteine, a glutathione precursor. Altogether, SelH protects against cellularsenescence to oxidative stress through a genome maintenance pathway involving ATM and p53. PMID:25336634

The plant G-protein network, comprising Gα, Gβ, and Gγ core subunits, regulates development, senses sugar, and mediates biotic and abiotic stress responses. Here, we report G-protein signalling in the salt stress response using two crop models, rice and maize. Loss-of-function mutations in the corresponding genes encoding the Gα subunit attenuate growth inhibition and cellularsenescence caused by sodium chloride (NaCl). Gα null mutations conferred reduced leaf senescence, chlorophyll degradation, and cytoplasm electrolyte leakage under NaCl stress. Sodium accumulated in both wild-type and Gα-mutant shoots to the same levels, suggesting that Gα signalling controls cell death in leaves rather than sodium exclusion in roots. Growth inhibition is probably initiated by osmotic change around root cells, because KCl and MgSO4 also suppressed seedling growth equally as well as NaCl. NaCl lowered rates of cell division and elongation in the wild-type leaf sheath to the level of the Gα-null mutants; however there was no NaCl-induced decrease in cell division in the Gα mutant, implying that the osmotic phase of salt stress suppresses cell proliferation through the inhibition of Gα-coupled signalling. These results reveal two distinct functions of Gα in NaCl stress in these grasses: attenuation of leaf senescence caused by sodium toxicity in leaves, and cell cycle regulation by osmotic/ionic stress. PMID:25227951

Ion channels play a major factor in maintaining cellular homeostasis but very little is known about the role of these proteins in cancer biology. In this work we have discovered that, the Kv11.3 (hERG3) a plasma-membrane potassium channel plays a critical role in the regulation of autophagy in a cancer cell model. We have found that pharmacologic stimulation of the Kv11.3 channel with a small molecule activator, NS1643 induced autophagy via activation of an AMPK-dependent signaling pathway in melanoma cell line. In addition, we have found that NS1643 produced a strong inhibition of cell proliferation by activating a cellularsenescence program. Furthermore, inhibition of autophagy via siRNA targeting AMPK or treatment with hydroxychloroquine an autophagy inhibitor activates apoptosis in NS1643-treated cells. Thus, we propose that, Kv11.3 is a novel mediator of autophagy, autophagy can be a survival mechanism contributing to cellularsenescence, and that use of a combinatorial pharmacologic approach of Kv11.3 activator with inhibitors of autophagy represents a novel therapeutic approach against melanoma. PMID:26942884

Sea urchins exhibit a very different life history from humans and short-lived model animals and therefore provide the opportunity to gain new insight into the complex process of aging. Sea urchins grow indeterminately, regenerate damaged appendages, and reproduce throughout their lifespan. Some species show no increase in mortality rate at advanced ages. Nevertheless, different species of sea urchins have very different reported lifespans ranging from 4 to more than 100 years, thus providing a unique model to investigate the molecular, cellular, and physiological mechanisms underlying both lifespan determination and negligible senescence. Studies to date have demonstrated maintenance of telomeres, maintenance of antioxidant and proteasome enzyme activities, and little accumulation of oxidative cellular damage with age in tissues of sea urchin species with different lifespans. Gene expression studies indicate that key cellular pathways involved in energy metabolism, protein homeostasis, and tissue regeneration are maintained with age. Taken together, these studies suggest that long-term maintenance of mechanisms that sustain tissue homeostasis and regenerative capacity is essential for indeterminate growth and negligible senescence, and a better understanding of these processes may suggest effective strategies to mitigate the degenerative decline in human tissues with age. PMID:26136616

Research highlights: {yields} Resveratrol induces cellularsenescence in glioma cell. {yields} Resveratrol inhibits mono-ubiquitination of histone H2B at K120. {yields} Depletion of RNF20, phenocopies the inhibitory effects of resveratrol. {yields} Mono-ubiquitination of histone H2B at K120 is a novel target of resveratrol. {yields} RNF20 inhibits cellularsenescence in proliferating glioma cells. -- Abstract: Resveratrol (3,4',5-trihydroxy-trans-stilbene), a polyphenol naturally occurring in grapes and other plants, has cancer chemo-preventive effects and therapeutic potential. Although resveratrol modulates multiple pathways in tumor cells, how resveratrol or its affected pathways converge on chromatin to mediate its effects is not known. Using glioma cells as a model, we showed here that resveratrol inhibited cell proliferation and induced cellular hypertrophy by transforming spindle-shaped cells to enlarged, irregular and flatten-shaped ones. We further showed that resveratrol-induced hypertrophic cells expressed senescence-associated-{beta}-galactosidase, suggesting that resveratrol-induced cellularsenescence in glioma cells. Consistent with these observations, we demonstrated that resveratrol inhibited clonogenic efficiencies in vitro and tumor growth in a xenograft model. Furthermore, we found that acute treatment of resveratrol inhibited mono-ubiquitination of histone H2B at K120 (uH2B) in breast, prostate, pancreatic, lung, brain tumor cells as well as primary human cells. Chronic treatment with low doses of resveratrol also inhibited uH2B in the resveratrol-induced senescent glioma cells. Moreover, we showed that depletion of RNF20, a ubiquitin ligase of histone H2B, inhibited uH2B and induced cellularsenescence in glioma cells in vitro, thereby recapitulated the effects of resveratrol. Taken together, our results suggest that uH2B is a novel direct or indirect chromatin target of resveratrol and RNF20 plays an important role in inhibiting cellular

Highlights: • Dyskerin depletion triggers cellularsenescence in U2OS osteosarcoma cells. • Dyskerin-depleted cells are resistant to apoptosis induced by genotoxic stress. • Chromatin relaxation sensitizes dyskerin-depleted cells to apoptosis. - Abstract: Dyskerin is a conserved, nucleolar RNA-binding protein implicated in an increasing array of fundamental cellular processes. Germline mutation in the dyskerin gene (DKC1) is the cause of X-linked dyskeratosis congenita (DC). Conversely, wild-type dyskerin is overexpressed in sporadic cancers, and high-levels may be associated with poor prognosis. It was previously reported that acute loss of dyskerin function via siRNA-mediated depletion slowed the proliferation of transformed cell lines. However, the mechanisms remained unclear. Using human U2OS osteosarcoma cells, we show that siRNA-mediated dyskerin depletion induced cellularsenescence as evidenced by proliferative arrest, senescence-associated heterochromatinization and a senescence-associated molecular profile. Senescence can render cells resistant to apoptosis. Conversely, chromatin relaxation can reverse the repressive effects of senescence-associated heterochromatinization on apoptosis. To this end, genotoxic stress-induced apoptosis was suppressed in dyskerin-depleted cells. In contrast, agents that induce chromatin relaxation, including histone deacetylase inhibitors and the DNA intercalator chloroquine, sensitized dyskerin-depleted cells to apoptosis. Dyskerin is a core component of the telomerase complex and plays an important role in telomere homeostasis. Defective telomere maintenance resulting in premature senescence is thought to primarily underlie the pathogenesis of X-linked DC. Since U2OS cells are telomerase-negative, this leads us to conclude that loss of dyskerin function can also induce cellularsenescence via mechanisms independent of telomere shortening.

Acute kidney injury is a major clinical problem and advanced age is associated with ineffective renal regeneration and poor functional outcome. Data from kidney injury models suggest that a loss of tubular epithelial proliferation contributes to a decrease in renal repair capacity with aging, but aging can also lead to a higher severity of inflammation and damage which may influence repair. In this study we tested intrinsic age-dependent changes in tubular epithelial proliferation in young and old mice, by injecting low-dose lead acetate as a non-injurious mitogen. In parallel, we explored in vitro techniques of studying cellularsenescence in primary tubular epithelial cells (PTEC). Lead acetate induced tubular epithelial proliferation at a significantly higher rate in young as compared to old mice. Old kidneys showed significantly more senescence as demonstrated by increased p16 (INK4a), senescence associated β-galactosidase, and γH2AX(+)/Ki-67(-) cells. This was paralleled in old kidneys by a higher number of Cyclin D1 positive tubular cells. This finding was corroborated by a positive correlation between Cyclin D1 positivity and age in human renal biopsies. When tubular cells were isolated from mouse kidneys they rapidly lost their age-associated differences under culture conditions. However, senescence was readily induced in PTEC by γ-irradiation representing a future model for study of cellularsenescence in the renal epithelium. Together, our data indicate that the tubular epithelium of aged kidney has an intrinsically reduced proliferative capacity probably due to a higher load of senescent cells. Moreover, stress induced models of cellularsenescence are preferable for study of the renal epithelium in vitro. Finally, the positive correlation of Cyclin D1 with age and cellularsenescence in PTEC needs further evaluation as to a functional role of renal epithelial aging. PMID:24505380

The cellular and subcellular localization of endogenous nitric oxide (NO˙) in leaves from young and senescent pea (Pisum sativum) plants was studied. Confocal laser scanning microscopy analysis of pea leaf sections with the fluorescent probe 4,5-diaminofluorescein diacetate revealed that endogenous NO˙ was mainly present in vascular tissues (xylem and phloem). Green fluorescence spots were also detected in the epidermal cells, palisade and spongy mesophyll cells, and guard cells. In senescent leaves, NO˙ generation was clearly reduced in the vascular tissues. At the subcellular level, by electron paramagnetic resonance spectroscopy with the spin trap Fe(MGD)2 and fluorometric analysis with 4,5-diaminofluorescein diacetate, NO˙ was found to be an endogenous metabolite of peroxisomes. The characteristic three-line electron paramagnetic resonance spectrum of NO˙, with g = 2.05 and aN = 12.8 G, was detected in peroxisomes. By fluorometry, NO˙ was also found in these organelles, and the level measured of NO˙ was linearly dependent on the amount of peroxisomal protein. The enzymatic production of NO˙ from l-Arg (nitric oxide synthase [NOS]-like activity) was measured by ozone chemiluminiscence. The specific activity of peroxisomal NOS was 4.9 nmol NO˙ mg−1 protein min−1; was strictly dependent on NADPH, calmodulin, and BH4; and required calcium. In senescent pea leaves, the NOS-like activity of peroxisomes was down-regulated by 72%. It is proposed that peroxisomal NO˙ could be involved in the process of senescence of pea leaves. PMID:15347796

Background Micro RNAs (miRs) have emerged as key regulators during oncogenesis. They have been found to regulate cell proliferation, differentiation, and apoptosis. Mir-125b has been identified as an oncomir in various forms of tumours, but we have previously proposed that miR-125b is a suppressor of lymph node metastasis in cutaneous malignant melanoma. Our goal was therefore to further examine this theory. Methods We used in-situ-hybridization to visualise miR-125b expression in primary tumours and in lymph node metastasis. Then using a miRVector plasmid containing a miR-125b-1 insert we transfected melanoma cell line Mel-Juso and then investigated the effect of the presence of a stable overexpression of miR-125b on growth by western blotting, flow cytometry and β-galactosidase staining. The tumourogenicity of the transfected cells was tested using a murine model and the tumours were further examined with in-situ-hybridization. Results In primary human tumours and in lymph node metastases increased expression of miR-125b was found in single, large tumour cells with abundant cytoplasm. A stable overexpression of miR-125b in human melanoma cell line Mel-Juso resulted in a G0/G1 cell cycle block and emergence of large cells expressing senescence markers: senescence-associated beta-galactosidase, p21, p27 and p53. Mel-Juso cells overexpressing miR-125b were tumourigenic in mice, but the tumours exhibited higher level of cell senescence and decreased expression of proliferation markers, cyclin D1 and Ki67 than the control tumours. Conclusions Our results confirm the theory that miR-125b functions as a tumour supressor in cutaneous malignant melanoma by regulating cellularsenescence, which is one of the central mechanisms protecting against the development and progression of malignant melanoma. PMID:24762088

Metformin, an oral hypoglycemic agent, has been used for decades to treat type 2 diabetes mellitus. Recent studies indicate that mice treated with metformin live longer and have fewer manifestations of age-related chronic disease. However, the molecular mechanisms underlying this phenotype are unknown. Here, we show that metformin treatment increases the levels of the microRNA-processing protein DICER1 in mice and in humans with diabetes mellitus. Our results indicate that metformin upregulates DICER1 through a post-transcriptional mechanism involving the RNA-binding protein AUF1. Treatment with metformin altered the subcellular localization of AUF1, disrupting its interaction with DICER1 mRNA and rendering DICER1 mRNA stable, allowing DICER1 to accumulate. Consistent with the role of DICER1 in the biogenesis of microRNAs, we found differential patterns of microRNA expression in mice treated with metformin or caloric restriction, two proven life-extending interventions. Interestingly, several microRNAs previously associated with senescence and aging, including miR-20a, miR-34a, miR-130a, miR-106b, miR-125, and let-7c, were found elevated. In agreement with these findings, treatment with metformin decreased cellularsenescence in several senescence models in a DICER1-dependent manner. Metformin lowered p16 and p21 protein levels and the abundance of inflammatory cytokines and oncogenes that are hallmarks of the senescence-associated secretory phenotype (SASP). These data lead us to hypothesize that changes in DICER1 levels may be important for organismal aging and to propose that interventions that upregulate DICER1 expression (e.g., metformin) may offer new pharmacotherapeutic approaches for age-related disease. PMID:26990999

The lipid microviscosity of microsomal membranes from senescing cut carnation (Dianthus caryophyllus L. cv. White Sim) flowers rises with advancing senescence. The increase in membrane microviscosity is initiated within 3 to 4 days of cutting the flowers and coincides temporally with petal-inrolling denoting the climacteric-like rise in ethylene production. Treatment of young cut flowers with aminoethoxyvinylglycine prevented the appearance of petal-inrolling and delayed the rise in membrane microviscosity until day 9 after cutting. When freshly cut flowers or aminoethoxyvinylglycine-treated flowers were exposed to exogenous ethylene (1 microliter per liter), the microviscosity of microsomal membranes rose sharply within 24 hours, and inrolling of petals was clearly evident. Thus, treatment with ethylene accelerates membrane rigidification. Silver thiosulphate, a potent anti-ethylene agent, delayed the rise in microsomal membrane microviscosity even when the flowers were exposed to exogenous ethylene. Membrane rigidification in both naturally senescing and ethylene-treated flowers was accompanied by an increased sterol:phospholipid ratio reflecting the selective loss of membrane phospholipid that accompanies senescence. The results collectively indicate that the climacteric-like surge in ethylene production during senescence of carnation flowers facilitates physical changes in membrane lipids that presumably lead to loss of membrane function. PMID:16662309

Cellularsenescence is an irreversible cell cycle arrest that limits the replicative lifespan of cells. Senescence suppresses development of tumors by regulating aging factors, such as cyclin dependent kinase inhibitor (CKI) and telomerase. Suppression subtractive hybridization (SSH) was used to identify genes that were differentially expressed between young human mesenchymal stem cells (Y-hMSCs) and senescent human mesenchymal stem cells (S-hMSCs). We selected positive clones that were functionally characterized by referring to public databases using NCBI BLAST tool. This search revealed that 19 genes were downregulated, and 43 genes were upregulated in S-hMSCs relative to Y-hMSCs. Among subtracted clones in Y-hMSCs, most of genes markedly were related to metabolic functions. These genes, PDIA3, WDR1, FSTL1, COPG1, LMAN1, and PDIA6, significantly downregulated. Conversely, genes for subtracted clones in S-hMSCs were mostly associated with cell adhesion. In particular, the expression levels of 9 genes, HSP90B1, EID1, ATP2B4, DDAH1, PRNP, RAB1A, PGS5, TM4SF1 and SSR3, gradually increased during senescence. These genes have not previously been identified as being related to cellularsenescence, but they seemed to be potentially affected during cellularsenescence. PMID:23466301

By activating the ataxia telangiectasia mutated (ATM)-mediated DNA Damage Response (DDR), the AMPK agonist metformin might sensitize cells against further damage, thus mimicking the precancerous stimulus that induces an intrinsic barrier against carcinogenesis. Herein, we present the new hypothesis that metformin might function as a tissue sweeper of pre-malignant cells before they gain stem cell/tumor initiating properties. Because enhanced glycolysis (the Warburg effect) plays a causal role in the gain of stem-like properties of tumor-initiating cells by protecting them from the pro-senescent effects of mitochondrial respiration-induced oxidative stress, metformin's ability to disrupt the glycolytic metabotype may generate a cellular phenotype that is metabolically protected against immortalization. The bioenergetic crisis imposed by metformin, which may involve enhanced mitochondrial biogenesis and oxidative stress, can lower the threshold for cellularsenescence by pre-activating an ATM-dependent pseudo-DDR. This allows an accelerated onset of cellularsenescence in response to additional oncogenic stresses. By pushing cancer cells to use oxidative phosphorylation instead of glycolysis, metformin can rescue cell surface major histocompatibility complex class I (MHC-I) expression that is downregulated by oncogenic transformation, a crucial adaptation of tumor cells to avoid the adaptive immune response by cytotoxic T-lymphocytes (CTLs). Aside from restoration of tumor immunosurveillance at the cell-autonomous level, metformin can activate a senescence-associated secretory phenotype (SASP) to reinforce senescence growth arrest, which might trigger an immune-mediated clearance of the senescent cells in a non-cell-autonomous manner. By diminishing the probability of escape from the senescence anti-tumor barrier, the net effect of metformin should be a significant decrease in the accumulation of dysfunctional, pre-malignant cells in tissues, including those with the

The coordination of cell cycle progression with the repair of DNA damage supports the genomic integrity of dividing cells. The function of many factors involved in DNA damage response (DDR) and the cell cycle depends on their Ran GTPase-regulated nuclear-cytoplasmic transport (NCT). The loading of Ran with GTP, which is mediated by RCC1, the guanine nucleotide exchange factor for Ran, is critical for NCT activity. However, the role of RCC1 or Ran⋅GTP in promoting cell proliferation or DDR is not clear. We show that RCC1 overexpression in normal cells increased cellular Ran⋅GTP levels and accelerated the cell cycle and DNA damage repair. As a result, normal cells overexpressing RCC1 evaded DNA damage-induced cell cycle arrest and senescence, mimicking colorectal carcinoma cells with high endogenous RCC1 levels. The RCC1-induced inhibition of senescence required Ran and exportin 1 and involved the activation of importin β-dependent nuclear import of 53BP1, a large NCT cargo. Our results indicate that changes in the activity of the Ran⋅GTP-regulated NCT modulate the rate of the cell cycle and the efficiency of DNA repair. Through the essential role of RCC1 in regulation of cellular Ran⋅GTP levels and NCT, RCC1 expression enables the proliferation of cells that sustain DNA damage. PMID:26864624

The coordination of cell cycle progression with the repair of DNA damage supports the genomic integrity of dividing cells. The function of many factors involved in DNA damage response (DDR) and the cell cycle depends on their Ran GTPase–regulated nuclear–cytoplasmic transport (NCT). The loading of Ran with GTP, which is mediated by RCC1, the guanine nucleotide exchange factor for Ran, is critical for NCT activity. However, the role of RCC1 or Ran⋅GTP in promoting cell proliferation or DDR is not clear. We show that RCC1 overexpression in normal cells increased cellular Ran⋅GTP levels and accelerated the cell cycle and DNA damage repair. As a result, normal cells overexpressing RCC1 evaded DNA damage–induced cell cycle arrest and senescence, mimicking colorectal carcinoma cells with high endogenous RCC1 levels. The RCC1-induced inhibition of senescence required Ran and exportin 1 and involved the activation of importin β–dependent nuclear import of 53BP1, a large NCT cargo. Our results indicate that changes in the activity of the Ran⋅GTP–regulated NCT modulate the rate of the cell cycle and the efficiency of DNA repair. Through the essential role of RCC1 in regulation of cellular Ran⋅GTP levels and NCT, RCC1 expression enables the proliferation of cells that sustain DNA damage. PMID:26864624

The retinoblastoma (RB)/p16INK4a pathway regulates senescence of human melanocytes in culture and oncogene-induced senescence of melanocytic nevi in vivo. This senescence response is likely due to chromatin modifications because RB complexes from senescent melanocytes contain increased levels of histone deacetylase (HDAC) activity and tethered HDAC1. Here we show that HDAC1 is prominently detected in p16INK4a-positive, senescent intradermal melanocytic nevi but not in proliferating, recurrent nevus cells that localize to the epidermal/dermal junction. To assess the role of HDAC1 in the senescence of melanocytes and nevi, we used tetracycline-based inducible expression systems in cultured melanocytic cells. We found that HDAC1 drives a sequential and cooperative activity of chromatin remodeling effectors, including transient recruitment of Brahma (Brm1) into RB/HDAC1 mega-complexes, formation of heterochromatin protein 1β (HP1β)/SUV39H1 foci, methylation of H3-K9, stable association of RB with chromatin and significant global heterochromatinization. These chromatin changes coincide with expression of typical markers of senescence, including the senescent-associated β-galactosidase marker. Notably, formation of RB/HP1β foci and early tethering of RB to chromatin depends on intact Brm1 ATPase activity. As cells reached senescence, ejection of Brm1 from chromatin coincided with its dissociation from HP1β/RB and relocalization to protein complexes of lower molecular weight. These results provide new insights into the role of the RB pathway in regulating cellularsenescence and implicate HDAC1 as a likely mediator of early chromatin remodeling events. PMID:17578512

We have utilized high-density GeneChip oligonucleotide arrays to investigate the use of the senescence-accelerated mouse (SAM) as a biogerontological resource to identify patterns of gene expression in the chemosensory-nasal mucosa. Gene profiling in chronologically young and old mice of the senescence-resistant (SAMR) and senescence-prone (SAMP) strains revealed 133 known genes that were modulated by a three-fold or greater change either in one strain or the other or in both strains during aging. We also identified known genes in our study which based on their encoded proteins were identified as aging-related genes in the aging neocortex and cerebellum of mice as reported by Lee et al. (2000) [Nat. Genet. 25 (2000) 294]. Changes in gene profiles for chemosensory-related genes including olfactory and vomeronasal receptors, sensory transduction-associated proteins, and odor and pheromone transport molecules in the young SAMR and SAMP were compared with age-matched C57BL/6J mice. An analysis of known gene expression profiles suggests that changes in the expression of immune factor genes and genes associated with cell cycle progression and cell death were particularly prominent in the old SAM strains. A preliminary cellular validation study supported the dysregulation of cell cycle-related genes in the old SAM strains. The results of our initial study indicated that the use of the SAM models of aging could provide substantive information leading to a more fundamental understanding of the aging process in the chemosensory-nasal mucosa at the genomic, molecular, and cellular levels. PMID:12605961

Age-related damage accumulates and a variety of biological activities and functions deteriorate in senescent cells. However, little is known about when cellular aging behaviors begin and what cellular aging processes change. Previous research demonstrated age-related mRNA changes in budding yeast by the 18th to 20th generation, which is the average replicative lifespan of yeast (i.e. about half of the population is dead by this time point). Here, we performed transcriptional and metabolic profiling for yeast at early stages of senescence (4th, 7th, and 11th generation), that is, for populations in which most cells are still alive. Transcriptional profiles showed up- and down-regulation for ∼20% of the genes profiled after the first four generations, few further changes by the 7th generation, and an additional 12% of the genes were up- and down-regulated after 11 generations. Pathway analysis revealed that these 11th generation cells had accumulated transcripts coding for enzymes involved in sugar metabolism, the TCA cycle, and amino acid degradation and showed decreased levels of mRNAs coding for enzymes involved in amino acid biosynthetic pathways. These observations were consistent with the metabolomic profiles of aging cells: an accumulation of pyruvic acid and TCA cycle intermediates and depletion of most amino acids, especially branched-chain amino acids. Stationary phase-induced genes were highly expressed after 11 generations even though the growth medium contained adequate levels of nutrients, indicating deterioration of the nutrient sensing and/or signaling pathways by the 11th generation. These changes are presumably early indications of replicative senescence. PMID:25294875

Ultraviolet (UV) irradiation causes damage in skin by generating excessive reactive oxygen species (ROS) and induction of matrix metalloproteinases (MMPs), leading to skin photoageing. Dandelion extracts have long been used for traditional Chinese medicine and native American medicine to treat cancers, hepatitis, and digestive diseases; however, less is known on the effects of dandelion extracts in skin photoageing. Here we found that dandelion leaf and flower extracts significantly protect UVB irradiation-inhibited cell viability when added before UVB irradiation or promptly after irradiation. Dandelion leaf and flower extracts inhibited UVB irradiation-stimulated MMP activity and ROS generation. Dandelion root extracts showed less action on protecting HDFs from UVB irradiation-induced MMP activity, ROS generation, and cell death. Furthermore, dandelion leaf and flower but not root extracts stimulated glutathione generation and glutathione reductase mRNA expression in the presence or absence of UVB irradiation. We also found that dandelion leaf and flower extracts help absorb UVB irradiation. In addition, dandelion extracts significantly protected HDFs from H2O2-induced cellularsenescence. In conclusion, dandelion extracts especially leaf and flower extracts are potent protective agents against UVB damage and H2O2-induced cellularsenescence in HDFs by suppressing ROS generation and MMP activities and helping UVB absorption. PMID:26576225

The amount of cellular proteins is a crucial parameter that is known to vary between cells as a function of the replicative passages, and can be important during physiological aging. The process of protein degradation is known to be performed by a series of enzymatic reactions, ranging from an initial step of protein ubiquitination to their final fragmentation by the proteasome. In this paper we propose a stochastic dynamical model of nuclear proteins concentration resulting from a balance between a constant production of proteins and their degradation by a cooperative enzymatic reaction. The predictions of this model are compared with experimental data obtained by fluorescence measurements of the amount of nuclear proteins in murine tail fibroblast (MTF) undergoing cellularsenescence. Our model provides a three-parameter stationary distribution that is in good agreement with the experimental data even during the transition to the senescent state, where the nuclear protein concentration changes abruptly. The estimation of three parameters (cooperativity, saturation threshold, and maximal velocity of the reaction), and their evolution during replicative passages shows that only the maximal velocity varies significantly. Based on our modeling we speculate the reduction of functionality of the protein degradation mechanism as a possible competitive inhibition of the proteasome. PMID:26115222

Ultraviolet (UV) irradiation causes damage in skin by generating excessive reactive oxygen species (ROS) and induction of matrix metalloproteinases (MMPs), leading to skin photoageing. Dandelion extracts have long been used for traditional Chinese medicine and native American medicine to treat cancers, hepatitis, and digestive diseases; however, less is known on the effects of dandelion extracts in skin photoageing. Here we found that dandelion leaf and flower extracts significantly protect UVB irradiation-inhibited cell viability when added before UVB irradiation or promptly after irradiation. Dandelion leaf and flower extracts inhibited UVB irradiation-stimulated MMP activity and ROS generation. Dandelion root extracts showed less action on protecting HDFs from UVB irradiation-induced MMP activity, ROS generation, and cell death. Furthermore, dandelion leaf and flower but not root extracts stimulated glutathione generation and glutathione reductase mRNA expression in the presence or absence of UVB irradiation. We also found that dandelion leaf and flower extracts help absorb UVB irradiation. In addition, dandelion extracts significantly protected HDFs from H2O2-induced cellularsenescence. In conclusion, dandelion extracts especially leaf and flower extracts are potent protective agents against UVB damage and H2O2-induced cellularsenescence in HDFs by suppressing ROS generation and MMP activities and helping UVB absorption. PMID:26576225

Normal cells in culture exhibit limited division potential and have been used as a model for cellularsenescence. In contrast, tumor-derived or carcinogen- or virus-transformed cells are capable of indefinite division. Fusion of normal human diploid fibroblasts with immortal human cells yielded hybrids having limited life spans, indicating that cellularsenescence was dominant. Fusions of various immortal human cell lines with each other led to the identification of four complementation groups for indefinite division. The purpose of this study was to determine whether human chromosome 1 could complement the recessive immortal defect of human cell lines assigned to one of the four complementation groups. Using microcell fusion, the authors introduced a single normal human chromosome 1 into immortal human cell lines representing the complementation groups and determined that it caused loss of proliferative potential of an osteosarcoma-derived cell line (TE85), a cytomegalovirus-transformed lung fibroblast cell line (CMV-Mj-HEL-1), and a Ki-ras[sup +]-transformed derivative of TE85 (143B TK[sup [minus

S-phase kinase-associated protein 2 (Skp2) belongs to the F-box protein family. It is a component of the SCF E3 ubiquitin ligase complex. Skp2 has been shown to regulate cellular proliferation by targeting several cell cycle-regulated proteins for ubiquitination and degradation, including cyclin-dependent kinase inhibitor p27. Skp2 has also been demonstrated to display an oncogenic function since its overexpression has been observed in many human cancers. This review discusses the recent discoveries on the novel roles of Skp2 in regulating cellularsenescence, cancer progression, and metastasis, as well as the therapeutic potential of targeting Skp2 for human cancer treatment. PMID:22200179

The relationship between brain glucose metabolism and learning deficit was examined in the senescence-accelerated-prone mouse (SAMP) 8, which has been proven to be a useful murine model of age-related behavioral disorders. SAMP8, 7 months old, exhibited marked learning impairment in the passive avoidance task, as compared with the control strain, senescence-accelerated-resistant mice (SAMR) 1. SAMP8 also exhibited a reduction in brain glucose metabolism, as indicated by a reduction in [14C]2-deoxyglucose accumulation in the brain following the intravenous injection impaired glucose metabolism correlated significantly with the learning impairment in all brain regions in SAMR1 and SAMP8. In the SAMP8, a significant correlation was observed in the posterior half of the cerebral cortex. These results suggest that the SAMP8 strain is a useful model of not only age-related behavioral disorders, but also glucose hypometabolism observed in aging and dementias. PMID:8905734

This data article contains the supporting information for the research article entitled "Early onset of behavioral alterations in senescence-accelerated mouse prone 8 (SAMP8)" [1]. Senescence-accelerated mouse prone 8 (SAMP8), which originally developed from AKR/J mice, shows learning and memory impairments at the age of 8-12 months. However, little information is still available on phenotypical characteristics of younger SAMP8. To fully understand the phenotype of younger SAMP8, we optimized two behavioral tasks for SAMP8. In the object recognition task, 4-month-old SAMP8 made significantly more contacts with the familiar objects compared to age-matched SAMR1, however, distance traveled for both strains of mice were comparable. In the fear conditioning task, conventionally-used CS-US combination failed to induce robust conditioned fear in both strains of mice. PMID:27331099

Progeroid syndromes show features of accelerated ageing and are used as models for human ageing, of which Werner syndrome (WS) is one of the most widely studied. WS fibroblasts show acceleratedsenescence that may result from p38 MAP kinase activation since it is prevented by the p38 inhibitor SB203580. Thus, small molecule inhibition of p38-signalling may be a therapeutic strategy for WS. To develop this approach issues such as the in vivo toxicity and kinase selectivity of existing p38 inhibitors need to be addressed, so as to strengthen the evidence that p38 itself plays a critical role in mediating the effect of SB203580, and to find an inhibitor suitable for in vivo use. In this work we used a panel of different p38 inhibitors selected for: (1) having been used successfully in vivo in either animal models or human clinical trials; (2) different modes of binding to p38; and (3) different off-target kinase specificity profiles, in order to critically address the role of p38 in the premature senescence seen in WS cells. Our findings confirmed the involvement of p38 in accelerated cell senescence and identified p38 inhibitors suitable for in vivo use in WS, with BIRB 796 the most effective. PMID:27136566

Progeroid syndromes show features of accelerated ageing and are used as models for human ageing, of which Werner syndrome (WS) is one of the most widely studied. WS fibroblasts show acceleratedsenescence that may result from p38 MAP kinase activation since it is prevented by the p38 inhibitor SB203580. Thus, small molecule inhibition of p38-signalling may be a therapeutic strategy for WS. To develop this approach issues such as the in vivo toxicity and kinase selectivity of existing p38 inhibitors need to be addressed, so as to strengthen the evidence that p38 itself plays a critical role in mediating the effect of SB203580, and to find an inhibitor suitable for in vivo use. In this work we used a panel of different p38 inhibitors selected for: (1) having been used successfully in vivo in either animal models or human clinical trials; (2) different modes of binding to p38; and (3) different off-target kinase specificity profiles, in order to critically address the role of p38 in the premature senescence seen in WS cells. Our findings confirmed the involvement of p38 in accelerated cell senescence and identified p38 inhibitors suitable for in vivo use in WS, with BIRB 796 the most effective. PMID:27136566

The Polycomb group protein Bmi-1 is an essential regulator of cellularsenescence and is believed to function largely through the direct repression of the Ink4a/Arf locus. However, concurrent deletion of Ink4a/Arf does not fully rescue the defects detected in Bmi-1(-/-) mice, indicating that additional Bmi-1 targets remain to be identified. The expression of the chromatin-associated Sin3B protein is stimulated by oncogenic stress, and is required for oncogene-induced senescence. Here we demonstrate that oncogenic stress leads to the dissociation of Bmi-1 from the Sin3B locus, resulting in increased Sin3B expression and subsequent entry into cellularsenescence. Furthermore, Sin3B is required for the senescent phenotype and elevated levels of reactive oxygen species elicited upon Bmi-1 depletion. Altogether, these results identify Sin3B as a novel direct target of Bmi-1, and establish Bmi-1-driven repression of Sin3B as an essential regulator of cellularsenescence. PMID:25263442

The Polycomb group protein Bmi-1 is an essential regulator of cellularsenescence and is believed to function largely through the direct repression of the Ink4a/Arf locus. However, concurrent deletion of Ink4a/Arf does not fully rescue the defects detected in Bmi-1−/− mice, indicating that additional Bmi-1 targets remain to be identified. The expression of the chromatin associated Sin3B protein is stimulated by oncogenic stress, and is required for oncogene-induced senescence. Here we demonstrate that oncogenic stress leads to the dissociation of Bmi-1 from the Sin3B locus, resulting in increased Sin3B expression and subsequent entry into cellularsenescence. Furthermore, Sin3B is required for the senescent phenotype and elevated levels of reactive oxygen species elicited upon Bmi-1 depletion. Altogether, these results identify Sin3B as a novel direct target of Bmi-1, and establish Bmi-1-driven repression of Sin3B as an essential regulator of cellularsenescence. PMID:25263442

The senescence-accelerated mouse (SAM) has been under development by our research team at Kyoto University since 1970 through selective inbreeding of the AKR/J strain of mice donated by the Jackson Laboratory in 1968, based on the data of the grading score of senescence, life span, and pathologic phenotypes. At present, there are 12 lines of SAM; the 9 senescence-prone inbred strains (SAMP) include SAMP1, SAMP2, SAMP3, SAMP6, SAMP7, SAMP8, SAMP9, SAMP10 and SAMP11, and the 3 senescence-resistant inbred strains (SAMR) SAMR1, SANR4 and SAMR5. Data from survival curves, the Gompertzian function and the grading score of senescence, together with growth patterns of body weight of these SAMP and SAMR mice revealed that the characteristic feature of aging common to all SAMP mice is "acceleratedsenescence": early onset and irreversible advance of senescence manifested by several signs and gross lesions such as the loss of normal behavior, various skin lesions, increased lordokyphosis, etc., after a period of normal development. Routine postmortem examinations and the pathobiological features revealed by systematically designed studies have shown several pathologic phenotypes, which are often characteristic enough to differentiate among the various SAM strains: senile amyloidosis in SAMP1, -P2, -P7, -P9, -P10 and -P11, secondary amyloidosis in SAMP2 and -P6, contracted kidney in SAMP1, -P2, -P10, -P11, immunoblastic lymphoma in SAMR1 and -R4, histiocytic sarcoma in SAMR1 and -R4, ovarian cysts in SAMR1, impaired immune response in SAMP1, -P2 and -P8, hyperinflation of the lungs in SAMP1, hearing impairment in SAMP1, degenerative temporomandibular joint disease in SAMP3, senile osteoporosis in SAMP6, deficits in learning and memory in SAMP8 and -P10, emotional disorders in SAMP8 and -P10, cataracts in SAMP9, and brain atrophy in SAMP10. These are all age-associated pathologies, the incidence and severity of which increase with advancing age. The SAM model in which these

Methylation of N-terminal arginines of the shelterin component TRF2 is important for cellular proliferation. While TRF2 is found at telomeres, where it plays an essential role in maintaining telomere integrity, little is known about the cellular localization of methylated TRF2. Here we report that the majority of methylated TRF2 is resistant to extraction by high salt buffer and DNase I treatment, indicating that methylated TRF2 is tightly associated with the nuclear matrix. We show that methylated TRF2 drastically alters its nuclear staining as normal human primary fibroblast cells approach and enter replicative senescence. This altered nuclear staining, which is found to be overwhelmingly associated with misshapen nuclei and abnormal nuclear matrix folds, can be suppressed by hTERT and it is barely detectable in transformed and cancer cell lines. We find that dysfunctional telomeres and DNA damage, both of which are potent inducers of cellularsenescence, promote the altered nuclear staining of methylated TRF2, which is dependent upon the ATM-mediated DNA damage response. Collectively, these results suggest that the altered nuclear staining of methylated TRF2 may represent ATM-mediated nuclear structural alteration associated with cellularsenescence. Our data further imply that methylated TRF2 can serve as a potential biomarker for cellularsenescence. PMID:24721747

Cellularsenescence of endothelial cells is a damage and stress response which induces pro-inflammatory, pro-atherosclerotic, and pro-thrombotic phenotypes. Donepezil is a drug used for the treatment of mild to moderate dementia of the Alzheimer's disease (AD). The aim of the present study was to investigate the attenuation of endothelial cell senescence by donepezil and to explore the mechanisms underlying the anti-aging effects of donepezil. Our results indicated that high glucose (HG) markedly decreased cell viability of human umbilical vein endothelial cells (HUVECs), and this phenomenon was reversed by treatment with donepezil. Importantly, our results displayed that the frequency of senescent (SA-ß-gal-positive) cells and the expression level of senescence genes (PAI-1 and p21) were significantly higher in the HG group compared with the normal glucose (NG) group, and these changes were blocked by treatment with donepezil. Also, our results showed that donepezil inhibits the generation of reactive oxygen species (ROS), which promotes cellularsenescence. Pretreatment with nicotinamide (NAM), a sirtuin 1 (SIRT1) inhibitor, inhibited the reduction in senescence associated with donepezil. Indeed, our results indicated that donepezil increased the SIRT1 enzyme activity. Therefore, these results show that donepezil delays cellularsenescence that is promoted under HG condition via activation of SIRT1. PMID:26194321

Purpose: We examined biological responses of human glioma cells to irradiation with carbon ion beams (C-ions). Methods and Materials: A human glioma-derived cell line, NP-2, was irradiated with C-ions. Apoptotic cell nuclei were stained with Hoechst 33342. Induction of autophagy was examined either by staining cells with monodansylcadaverine (MDC) or by Western blotting to detect conversion of microtuble-associated protein light chain 3 (MAP-LC3) (LC3-I) to the membrane-bound form (LC3-II). Cellularsenescence markers including induction of senescence-associated beta-galactosidase (SA-beta-gal) were examined. The mean telomere length of irradiated cells was determined by Southern blot hybridization. Expression of tumor suppressor p53 and cyclin/cyclin-dependent kinase inhibitor p21{sup WAF1/CIP1} in the irradiated cells was analyzed by Western blotting. Results: When NP-2 cells were irradiated with C-ions at 6 Gy, the major population of the cells died of apoptosis and autophagy. The residual fraction of attached cells (<1% of initially irradiated cells) could not form a colony: however, they showed a morphological phenotype consistent with cellularsenescence, that is, enlarged and flattened appearance. The senescent nature of these attached cells was further indicated by staining for SA-beta-gal. The mean telomere length was not changed after irradiation with C-ions. Phosphorylation of p53 at serine 15 as well as the expression of p21{sup WAF1/CIP1} was induced in NP-2 cells after irradiation. Furthermore, we found that irradiation with C-ions induced cellularsenescence in a human glioma cell line lacking functional p53. Conclusions: Irradiation with C-ions induced apoptosis, autophagy, and cellularsenescence in human glioma cells.

LMNA mutations are responsible for a variety of genetic disorders, including muscular dystrophy, lipodystrophy, and certain progeroid syndromes, notably Hutchinson-Gilford Progeria. Although a number of clinical features of these disorders are suggestive of accelerated aging, it is not known whether cells derived from these patients exhibit cellular phenotypes associated with accelerated aging. We examined a series of isogenic skin fibroblast lines transfected with LMNA constructs bearing known pathogenic point mutations or deletion mutations found in progeroid syndromes. Fibroblasts overexpressing mutant lamin A exhibited accelerated rates of loss of telomeres and shortened replicative lifespans, in addition to abnormal nuclear morphology. To our surprise, these abnormalities were also observed in lines overexpressing wild-type lamin A. Copy number variants are common in human populations; those involving LMNA, whether arising meiotically or mitotically, might lead to progeroid phenotypes. In an initial pilot study of 23 progeroid cases without detectable WRN or LMNA mutations, however, no cases of altered LMNA copy number were detected. Nevertheless, our findings raise a hypothesis that changes in lamina organization may cause accelerated telomere attrition, with different kinetics for overexpession of wild-type and mutant lamin A, which leads to rapid replicative senescence and progroid phenotypes.

The SAM strain of mice is actually a group of related inbred strains consisting of series of SAMP (acceleratedsenescence-prone, short-lived) and SAMR (acceleratedsenescence-resistant, longer-lived) strains. Comparing with the SAMR strains, the SAMP strains of mice show a more acceleratedsenescence process, shorter lifespan, and an earlier onset and more rapid progress of age-associated pathological phenotypes similar to several geriatric disorders observed in humans, including senile osteoporosis, degenerative joint disease, age-related deficits in learning and memory, olfactory bulb and forebrain atrophy, presbycusis and retinal atrophy, senile amyloidosis, immunosenescence, senile lungs, and diffuse medial thickening of the aorta. The higher oxidative stress observed in the SAMP strains of mice are partly caused by mitochondrial dysfunction, and may be one cause of the senescenceacceleration and age-dependent alterations in cell structure and function, including neuronal cell degeneration. This senescenceacceleration is also observed during senescence/crisis in cultures of isolated fibroblast-like cells from SAMP strains of mice, and was associated with a hyperoxidative status. These observations suggest that the SAM strains are useful tools in the attempt to understand the mechanisms of age-dependent degeneration of cells and tissues, and their aggravation, and to develop clinical interventions. PMID:12470893

The endoplasmic reticulum (ER) is a multifunctional organelle critical for the proper folding and assembly of secreted and transmembrane proteins. Perturbations of ER functions cause ER stress, which activates a coordinated system of transcriptional and translational controls called the unfolded protein response (UPR), to cope with accumulation of misfolded proteins and proteotoxicity. It results in ER homeostasis restoration or in cell death. Senescence is a complex cell phenotype induced by several stresses such as telomere attrition, DNA damage, oxidative stress, and activation of some oncogenes. It is mainly characterized by a cell enlargement, a permanent cell-cycle arrest, and the production of a secretome enriched in proinflammatory cytokines and components of the extracellular matrix. Senescent cells accumulate with age in tissues and are suspected to play a role in age-associated diseases. Since senescence is a stress response, the question arises of whether an ER stress could occur concomitantly with senescence and participate in the onset or maintenance of the senescent features. Here, we described the interconnections between the UPR signaling and the different aspects of the cellularsenescence programs and discuss the implication of UPR modulations in this context. PMID:25540175

Senescence-accelerated mouse prone (SAMP) strains of mice show early onset of senescence, whereas senescence-accelerated mouse resistant (SAMR) strains are resistant to early senescence and serve as controls. Although SAMP6 and SAMP8 are established models of central nervous system alterations, it is unclear whether SAMP1/Sku (SAMP1) is characterized by brain alterations and dysfunction related to behavioral functioning. In the present study, behavioral tests (i.e., locomotor activity, Y-maze, rotating rod, hind-limb extension, and traction), histochemistry, and Western blot analyses were employed to study this mouse model using 2- and 4-month-old SAMP1 and age-matched control SAMR1. Although 2-month-old SAMP1 and SAMR1 showed similar activity, 4-month-old SAMP1 exhibited less activity than age-matched SAMR1 in locomotor activity and Y-maze tests. In rotating rod test, 2- and 4-month-old SAMP1 showed motor-coordination dysfunction. An abnormal extension reflex in the hind-limb test was observed in 2- and 4-month-old SAMP1. There were no significant differences between SAMP1 and SAMR1 with respect to grip strength in the traction test or alternation behavior in the Y-maze test. Histochemistry and Western blot analyses exhibited that cerebellar Purkinje cells in 4-month-old SAMP1 mice persistently expressed tyrosine hydroxylase. These results suggest that SAMP1 is a useful model for examining mechanisms underlying motor dysfunction. PMID:23583482

Head and neck cancer patients treated by radiation commonly suffer from a devastating side effect known as dry-mouth syndrome, which results from the irreversible loss of salivary gland function via mechanisms that are not completely understood. In this study, we used a mouse model of radiation-induced salivary hypofunction to investigate the outcomes of DNA damage in the head and neck region. We demonstrate that the loss of salivary function was closely accompanied by cellularsenescence, as evidenced by a persistent DNA damage response (γH2AX and 53BP1) and the expression of senescence-associated markers (SA-βgal, p19ARF, and DcR2) and secretory phenotype (SASP) factors (PAI-1 and IL6). Notably, profound apoptosis or necrosis was not observed in irradiated regions. Signs of cellularsenescence were also apparent in irradiated salivary glands surgically resected from human patients who underwent radiotherapy. Importantly, using IL6 knockout mice, we found that sustained expression of IL6 in the salivary gland long after initiation of radiation-induced DNA damage was required for both senescence and hypofunction. Additionally, we demonstrate that IL6 pretreatment prevented both senescence and salivary gland hypofunction via a mechanism involving enhanced DNA damage repair. Collectively, these results indicate that cellularsenescence is a fundamental mechanism driving radiation-induced damage in the salivary gland and suggest that IL6 pretreatment may represent a promising therapeutic strategy to preserve salivary gland function in head and neck cancer patients undergoing radiotherapy. PMID:26759233

Oxidative stress and persistent activation of DNA damage response (DDR) are causally involved in the development of cellularsenescence, a phenomenon implicated in fundamental (patho)physiological processes such as aging, fetal development and tumorigenesis. Here, we report that adenine nucleotide translocase-2 (ANT2) is consistently down-regulated in all three major forms of cellularsenescence: replicative, oncogene-induced and drug-induced, in both normal and cancerous human cells. We previously reported formation of novel NF1/Smad transcription repressor complexes in growth-arrested fibroblasts. Here we show that such complexes form in senescent cells. Mechanistically, binding of the NF1/Smad complexes to the NF1-dependent repressor elements in the ANT2 gene promoter repressed ANT2 expression. Etoposide-induced formation of these complexes and repression of ANT2 were relatively late events co-incident with production and secretion of, and dependent on, TGF-β. siRNA-mediated knock-down of ANT2 in proliferating cells resulted in increased levels of reactive oxygen species (ROS) and activation of the DDR. Knock-down of ANT2, together with etoposide treatment, further intensified ROS production and DNA damage signaling, leading to enhanced apoptosis. Together, our data show that TGF-β-mediated suppression of ANT2 through NF1/Smad4 complexes contributes to oxidative stress and DNA damage during induction of cellularsenescence. PMID:25220407

Ultraviolet (UV) irradiation generates reactive oxygen species (ROS) in the cells, which induces the cellularsenescence and photoaging. The present study investigated the protective effects of garlic on photo-damage and cellularsenescence in UVB-exposed human keratinocytes, HaCaT cells. An in vitro cell free system was used to examine the scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals and nitric oxide (NO). The effect of garlic extract on ROS formation, MMP-1 protein and mRNA expressions, cytokines such as interleukin (IL)-1β and IL-6, senescence associated-β-galactosidase (SA-β-gal) activity, and silent information regulator T1 (SIRT1) activity were determined in UVB-irradiated HaCaT cells. Garlic exhibited strong DPPH radical and NO scavenging activity in cell free system exhibiting IC50 values of 2.50 mg/mL and 4.38 mg/mL, respectively. Garlic pretreatment attenuated the production of UVB-induced intracellular ROS. MMP-1 level, which has been known to be induced by ROS, was dramatically elevated by UVB irradiation, and UVB-induced MMP-1 mRNA and protein expressions were significantly reduced by garlic treatment (50 µg/mL) comparable to those of UV-unexposed control cells. UV-induced pro-inflammatory cytokine productions (IL-6 and IL-1β) were significantly inhibited by pretreatment with garlic in a dose-dependent manner. SA-β-gal activity, a classical biomarker of cellularsenescence, and SIRT1 activity, which has attracted attention as an anti-aging factor in recent years, were ameliorated by garlic treatment in UV-irradiated HaCaT cells. The present study provides the first evidence of garlic inhibiting UVB-induced photoaging as a result of augmentation of cellularsenescence in HaCaT human keratinocytes. PMID:27483310

E2F1 and FOXO3 are two transcription factors that have been shown to participate in cellularsenescence. Previous report reveals that E2F1 enhanced cellularsenescence in human fibroblast cells, while FOXO transcription factors play against senescence by regulation reactive oxygen species scavenging proteins. However, their functional interplay has been unclear. Here we use E2F1 knock-out murine Embryonic fibroblasts (MEFs), knockdown RNAi constructs, and ectopic expression of E2F1 to show that it functions by negatively regulating FOXO3. E2F1 attenuates FOXO3-mediated expression of MnSOD and Catalase without affecting FOXO3 protein stability, subcellular localization, or phosphorylation by Akt. We mapped the interaction between E2F1 and FOXO3 to a region including the DNA binding domain of E2F1 and the C-terminal transcription-activation domain of FOXO3. We propose that E2F1 inhibits FOXO3-dependent transcription by directly binding FOXO3 in the nucleus and preventing activation of its target genes. Moreover, knockdown of the Caenorhabditis elegans E2F1 ortholog efl-1 significantly extends lifespan in a manner that requires the activity of the C. elegans FOXO gene daf-16. We conclude that there is an evolutionarily conserved signaling connection between E2F1 and FOXO3, which regulates cellularsenescence and aging by regulating the activity of FOXO3. We speculate that drugs and/or therapies that inhibit this physical interaction might be good candidates for reducing cellularsenescence and increasing longevity. PMID:25344604

Ultraviolet (UV) irradiation generates reactive oxygen species (ROS) in the cells, which induces the cellularsenescence and photoaging. The present study investigated the protective effects of garlic on photo-damage and cellularsenescence in UVB-exposed human keratinocytes, HaCaT cells. An in vitro cell free system was used to examine the scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals and nitric oxide (NO). The effect of garlic extract on ROS formation, MMP-1 protein and mRNA expressions, cytokines such as interleukin (IL)-1β and IL-6, senescence associated-β-galactosidase (SA-β-gal) activity, and silent information regulator T1 (SIRT1) activity were determined in UVB-irradiated HaCaT cells. Garlic exhibited strong DPPH radical and NO scavenging activity in cell free system exhibiting IC50 values of 2.50 mg/mL and 4.38 mg/mL, respectively. Garlic pretreatment attenuated the production of UVB-induced intracellular ROS. MMP-1 level, which has been known to be induced by ROS, was dramatically elevated by UVB irradiation, and UVB-induced MMP-1 mRNA and protein expressions were significantly reduced by garlic treatment (50 µg/mL) comparable to those of UV-unexposed control cells. UV-induced pro-inflammatory cytokine productions (IL-6 and IL-1β) were significantly inhibited by pretreatment with garlic in a dose-dependent manner. SA-β-gal activity, a classical biomarker of cellularsenescence, and SIRT1 activity, which has attracted attention as an anti-aging factor in recent years, were ameliorated by garlic treatment in UV-irradiated HaCaT cells. The present study provides the first evidence of garlic inhibiting UVB-induced photoaging as a result of augmentation of cellularsenescence in HaCaT human keratinocytes. PMID:27483310

Idiopathic pulmonary fibrosis (IPF) is a destructive disease in part resulting from premature or mature cellular aging. Protease-activated receptor-1 (PAR-1) recently emerged as a critical component in the context of fibrotic lung diseases. Therefore, we aimed to study the role of macrophages in PAR-1-mediated idiopathic pulmonary fibrosis. The number of macrophages were significantly reduced in lungs of PAR-1 antagonist (P1pal-12) treated animals upon bleomycin instillation. In line with these data, PAR-1 stimulation increased monocyte/macrophage recruitment in response to epithelium injury in in vitro trans-well assays. Moreover, macrophages induced fibroblasts migration, differentiation and secretion of collagen, which were inhibited in the presence of TGF-β receptor inhibitors. Interestingly, these profibrotic effects were partially inhibited by treatment with the PAR-1 inhibitor P1pal-12. Using shRNA mediated PAR-1 knock down in fibroblasts, we demonstrate that fibroblast PAR-1 contributes to TGF-β activation and production. Finally, we show that the macrophage-dependent induction of PAR-1 driven TGF-β activation was mediated by FXa. Our data identify novel mechanisms by which PAR-1 stimulation on different cell types can contribute to IPF and identify macrophages as key players in PAR-1 dependent development of this devastating disease. IPF may result from cellularsenescence mediated by macrophages in the lung. PMID:26474459

Senescenceaccelerated mouse (SAM), a murine model of acceleratedsenescence, was established by Toshio Takeda and colleagues. SAM consists of series of SAMP (prone) and SAMR (resistant) lines. All SAMP lines (from SAMP1 to SAMP11) are characterized by accelerated accumulation of senile features, earlier onset and faster progress of age-associated pathological phenotypes, such as amyloidosis, impaired immune response, senile osteoporosis and deficits in learning and memory. These SAMP lines are useful for evaluation of putative anti-aging therapies. For example, SAMP1 line is used to study the anti-aging effect of the antioxidant containing foods and various anti-oxidants, such as coenzyme Q10, vitamin C, lycopene. SAMP8 line exhibiting an early onset of impaired learning and memory is often used for test strategies for therapeutic intervention of dementia of early onset. SAMP6 is used as an animal model for developing new strategies for the treatment of osteoporosis in humans. Various lines of SAM (P1, P6, P8, P10 and R1) are now commercially available for research. In this review, I will briefly introduce various usages of SAM in anti-aging research. PMID:20046059

The senescence-accelerated prone 8 (SAMP8) mouse strain shows early cognitive loss that mimics the deterioration of learning and memory in the elderly and is widely used as an animal model of aging. SAMP8 mouse brain suffers oxidative stress, as well as tau- and amyloid-related pathology. Mitochondrial dysfunction and the subsequent increase in cellular oxidative stress are central to the aging processes of the organism. Here, we examined the mitochondrial status of neocortical neurons cultured from SAMP8 and senescence-accelerated-resistant (SAMR1) mice. SAMP8 mouse mitochondria showed a reduced membrane potential and higher vulnerability to inhibitors and uncouplers than SAMR1 mitochondria. DL-buthionine-[S,R]-sulfoximine (BSO) caused greater oxidative damage in neurons from SAMP8 mice than in those from SAMR1 mice. This increased vulnerability, indicative of frailty-associated senescence, was protected by the anti-aging agents melatonin and resveratrol. The sirtuin 1 inhibitor, sirtinol, demonstrated that the neuroprotection against BSO was partially mediated by increased sirtuin 1 expression. Melatonin, like resveratrol, enhanced sirtuin 1 expression in neuron cultures of SAMR1 and SAMP8 mice. Therefore, a deficiency in the neuroprotection and longevity of the sirtuin 1 pathway in SAMP8 neurons may contribute to the early age-related brain damage in these mice. This supports the therapeutic use of sirtuin 1-enhancing agents against age-related nerve cell dysfunction and brain frailty. PMID:22085194

Oral squamous cell carcinoma (OSCC) is the most common malignancy of head and neck. Although radiotherapy is used for OSCC treatment, the occurrence of radioresistant cancer cells limits its efficiency. MicroRNAs (miRNAs) are non-coding RNAs with lengths of 18-25 base pairs and known to be involved in carcinogenesis. We previously demonstrated that by targeting B lymphoma Mo-MLV insertion region 1 homolog (Bmi1), miR-494-3p functions as a putative tumor suppressor miRNA in OSCC. In this study, we further discovered that miR-494-3p could enhance the radiosensitivity of SAS OSCC cells and induce cellularsenescence. The overexpression of miR-494-3p in SAS cells increased the population of senescence-associated β-galactosidase positive cells, the expression of p16(INK4a) and retinoblastoma 1 (RB1), as well as downregulated Bmi1. The knockdown of Bmi1 by lentiviral-mediated delivery of specific short hairpin RNAs (shRNAs) also enhanced the radiosensitivity of SAS cells and the activation of the senescence pathway. Furthermore, the inverse correlation between Bmi1 and miR-494-3p expression was observed among OSCC tissues. Results suggest that miR-494-3p could increase the radiosensitivity of OSCC cells through the induction of cellularsenescence caused by the downregulation of Bmi1. PMID:27399693

Highlights: {yields} Overexpression of HDAC1 induces Sp1 deacetylation and raises Sp1/p300 complex formation to bind to PP2Ac promoter. {yields} Overexpression of HDAC1 strongly inhibits the phosphorylation of pRb through up-regulation of PP2A. {yields} Overexpressed HDAC1 restrains cell proliferaction and induces cell senescence though a novel Sp1/PP2A/pRb pathway. -- Abstract: Senescence is associated with decreased activities of DNA replication, protein synthesis, and cellular division, which can result in deterioration of cellular functions. Herein, we report that the growth and division of tumor cells were significantly repressed by overexpression of histone deacetylase (HDAC) 1 with the Tet-off induced system or transient transfection. In addition, HDAC1 overexpression led to senescence through both an accumulation of hypophosphorylated active retinoblastoma protein (pRb) and an increase in the protein level of protein phosphatase 2A catalytic subunit (PP2Ac). HDAC1 overexpression also increased the level of Sp1 deacetylation and elevated the interaction between Sp1 and p300, and subsequently that Sp1/p300 complex bound to the promoter of PP2Ac, thus leading to induction of PP2Ac expression. Similar results were obtained in the HDAC1-Tet-off stable clone. Taken together, these results indicate that HDAC1 overexpression restrained cell proliferation and induced premature senescence in cervical cancer cells through a novel Sp1/PP2A/pRb pathway.

Oral squamous cell carcinoma (OSCC) is the most common malignancy of head and neck. Although radiotherapy is used for OSCC treatment, the occurrence of radioresistant cancer cells limits its efficiency. MicroRNAs (miRNAs) are non-coding RNAs with lengths of 18–25 base pairs and known to be involved in carcinogenesis. We previously demonstrated that by targeting B lymphoma Mo-MLV insertion region 1 homolog (Bmi1), miR-494-3p functions as a putative tumor suppressor miRNA in OSCC. In this study, we further discovered that miR-494-3p could enhance the radiosensitivity of SAS OSCC cells and induce cellularsenescence. The overexpression of miR-494-3p in SAS cells increased the population of senescence-associated β-galactosidase positive cells, the expression of p16INK4a and retinoblastoma 1 (RB1), as well as downregulated Bmi1. The knockdown of Bmi1 by lentiviral-mediated delivery of specific short hairpin RNAs (shRNAs) also enhanced the radiosensitivity of SAS cells and the activation of the senescence pathway. Furthermore, the inverse correlation between Bmi1 and miR-494-3p expression was observed among OSCC tissues. Results suggest that miR-494-3p could increase the radiosensitivity of OSCC cells through the induction of cellularsenescence caused by the downregulation of Bmi1. PMID:27399693

Irreversible cell growth arrest, a process termed cellularsenescence, is emerging as an intrinsic tumor suppressive mechanism. Oncogene-induced senescence is thought to be invariably preceded by hyperproliferation, aberrant replication, and activation of a DNA damage checkpoint response (DDR), rendering therapeutic enhancement of this process unsuitable for cancer treatment. We previously demonstrated in a mouse model of prostate cancer that inactivation of the tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (Pten) elicits a senescence response that opposes tumorigenesis. Here, we show that Pten-loss–induced cellularsenescence (PICS) represents a senescence response that is distinct from oncogene-induced senescence and can be targeted for cancer therapy. Using mouse embryonic fibroblasts, we determined that PICS occurs rapidly after Pten inactivation, in the absence of cellular proliferation and DDR. Further, we found that PICS is associated with enhanced p53 translation. Consistent with these data, we showed that in mice p53-stabilizing drugs potentiated PICS and its tumor suppressive potential. Importantly, we demonstrated that pharmacological inhibition of PTEN drives senescence and inhibits tumorigenesis in vivo in a human xenograft model of prostate cancer. Taken together, our data identify a type of cellularsenescence that can be triggered in nonproliferating cells in the absence of DNA damage, which we believe will be useful for developing a “pro-senescence” approach for cancer prevention and therapy. PMID:20197621

Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is an RNA-binding protein that modulates splice site usage, polyadenylation, and cleavage efficiency. This protein has also been implicated in mRNA stability and transport from the nucleus. We have previously demonstrated that hnRNP A1 had diminished protein levels and showed cytoplasmic accumulation in senescent human diploid fibroblasts. Furthermore, we have shown that inhibition of p38 MAPK, a key regulator of cellularsenescence, elevated hnRNP A1 protein levels and inhibited hnRNP A1 cytoplasmic localization. In this study, we have explored the possible involvement of MNK1, one of the downstream effector of p38 MAPK, in the regulation of hnRNP A1. We have demonstrated that pharmacological inhibition of MNK1 by CGP 57380 decreased the phosphorylation levels of hnRNP A1 in young and senescent fibroblast cells and blocked the cytoplasmic accumulation of hnRNP A1 in senescent cells. In addition, MNK1 formed a complex with hnRNP A1 in vivo. The expression levels of MNK1, phospho-MNK1, and phospho-eIF4E proteins were found to be elevated in senescent cells. These data suggest that MNK1 regulates the phosphorylation and the subcellular distribution of hnRNP A1 and that MNK1 may play a role in the induction of senescence. -- Highlights: Black-Right-Pointing-Pointer MNK1 and not MAPKAPK2 phosphorylates hnRNP A1. Black-Right-Pointing-Pointer MNK1 has elevated levels in senescent cells, this has not been reported previously. Black-Right-Pointing-Pointer MNK1 activity induces cytoplasmic accumulation of hnRNP A1 in senescent cells. Black-Right-Pointing-Pointer Altered cytoplasmic localization of hnRNP A1 may alter gene expression patterns. Black-Right-Pointing-Pointer Our studies may increase our understanding of RNA metabolism during cellular aging.

To elucidate the fundamental mechanism of age-related deficiencies of learning and to develop effective drugs for intervention in age-related diseases such as learning dysfunctions, pertinent animal models that have characteristics closely similar to human dysfunctions should be established. SAM (senescence-accelerated mouse) has been established as a murine model of the SAM strains, groups of related inbred strains including nine strains of acceleratedsenescence-prone, short-lived mice (SAMP) and three strains of acceleratedsenescence-resistant, long-lived mice (SAMR). SAMP-strain mice show relatively strain-specific age-associated phenotypic pathologies such as shortened life span and early manifestation of senescence. Among the SAMP-strain mice, SAMP8 mice show an age-related deterioration in learning ability. Here, the neuropathological, neurochemical and pharmacological features of SAM are reported, especially for SAMP8. Moreover, the effects of several drugs on the biochemical and behavioral alterations in SAMP8 and the etiologic manifestation of acceleratedsenescence are also discussed. PMID:9920195

During aging, levels of testosterone gradually decline in men and low levels of testosterone in aged men are accompanied by increased incidence of depressive disorders. The senescence-accelerated-prone mouse 10 (SAMP10) is well known as an animal model of aging. The purpose of this study was to investigate the motor function, anxiety levels, depression-related emotional responses, attentional function and plasma levels of testosterone and dehydroepiandrosterone (DHEA) in SAMP10. SAMP10 exhibited a significant prolongation of immobility time compared to that of the aged-matched control senescence-accelerated-resistant mouse 1 (SAMR1) in the tail suspension test for measuring depression. Moreover, significant low levels of plasma testosterone but not DHEA were found in SAMP10, and the testosterone levels were inversely correlated with the depression-like behavior. By contrast, we did not observe any significant differences between SAMP10 and SAMR1 in the open-field, rota-rod, elevated plus-maze, marble-burying behavior, or prepulse inhibition test. The results of the present study indicate that testosterone may play an important role in the depression-like behavior in SAMP10. PMID:20117148

The constituents of the ethanol extract from the root of Polygala tenuifolia Willd. (Polygalaceae) were investigated for antioxidant activity in senescence-accelerated mice. Consequently, two relevant samples were obtained, a fraction separated by macroporous resin (YZ-OE), and a major pure crystal of 3,6'-disinapoyl sucrose (DISS). Based on HPLC-ESI-MS analysis, the most constituents in the YZ-OE fraction from the extract of P. tenuifolia were oligosaccharide esters. The antioxidant activities of these two samples were evaluated using the acceleratedsenescence-prone, short-lived mice (SAMP) in vivo. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) were increased significantly in SAMP mice fed oligosaccharide esters (YZ-OE 50 mg/kg) and its constituents (DISS 50 mg/kg). However, the content of malondialdehyde (MDA) was increased in the blood and liver of SAMP mice. But when given YZ-OE, it could be decreased, by 44.3% and 47.5%, respectively, compared with the SAMP model. Results from the analyses indicated that the oligosaccharide esters (YZ-OE) from roots of P. tenuifolia had a high in vivo antioxidant activity. PMID:20645784

Sirtuins (SIRT) belonging to the NAD+ dependent histone deacetylase III class of enzymes have emerged as master regulators of metabolism and longevity. However, their role in prevention of organismal aging and cellularsenescence still remains controversial. In the present study, we now report upregulation of SIRT2 as a specific feature associated with stress induced premature senescence but not with either quiescence or cell death. Additionally, increase in SIRT2 expression was noted in different types of senescent conditions such as replicative and oncogene induced senescence using multiple cell lines. Induction of SIRT2 expression during senescence was dependent on p53 status as depletion of p53 by shRNA prevented its accumulation. Chromatin immunoprecipitation revealed the presence of p53 binding sites on the SIRT2 promoter suggesting its regulation by p53, which was also corroborated by the SEAP reporter assay. Overexpression or knockdown of SIRT2 had no effect on stress induced premature senescence, thereby indicating that SIRT2 increase is not a cause of senescence; rather it is an effect linked to senescence-associated changes. Overall, our results suggest SIRT2 as a promising marker of cellularsenescence at least in cells with wild type p53 status. PMID:27229617

The role of cellularsenescence (CS) in age-related diseases (ARDs) is a quickly emerging topic in aging research. Our comprehensive data mining revealed over 250 genes tightly associated with CS. Using systems biology tools, we found that CS is closely interconnected with aging, longevity and ARDs, either by sharing common genes and regulators or by protein-protein interactions and eventually by common signaling pathways. The most enriched pathways across CS, ARDs and aging-associated conditions (oxidative stress and chronic inflammation) are growth-promoting pathways and the pathways responsible for cell-extracellular matrix interactions and stress response. Of note, the patterns of evolutionary conservation of CS and cancer genes showed a high degree of similarity, suggesting the co-evolution of these two phenomena. Moreover, cancer genes and microRNAs seem to stand at the crossroad between CS and ARDs. Our analysis also provides the basis for new predictions: the genes common to both cancer and other ARD(s) are highly likely candidates to be involved in CS and vice versa. Altogether, this study shows that there are multiple links between CS, aging, longevity and ARDs, suggesting a common molecular basis for all these conditions. Modulating CS may represent a potential pro-longevity and anti-ARDs therapeutic strategy. PMID:22184282

DNA-damage induces a DNA-damage response (DDR) in mammalian cells. The response, depending upon the cell-type and the extent of DNA-damage, ultimately results in cell death or cellularsenescence. DDR-induced signaling in cells activates the ATM-p53 and ATM-IKKα/β-interferon (IFN)-β signaling pathways, thus leading to an induction of the p53 and IFN-inducible IFI16 gene. Further, upon DNA-damage, DNA accumulates in the cytoplasm, thereby inducing the IFI16 protein and STING-dependent IFN-β production and activation of the IFI16 inflammasome, resulting in the production of proinflammatory cytokines (e.g., IL-1β and IL-18). Increased expression of IFI16 protein in a variety of cell-types promotes cellularsenescence. However, reduced expression of IFI16 in cells promotes cell proliferation. Because expression of the IFI16 gene is induced by activation of DNA-damage response in cells and increased levels of IFI16 protein in cells potentiate the p53-mediated transcriptional activation of genes and p53 and pRb-mediated cell cycle arrest, we discuss how an improved understanding of the role of IFI16 protein in cellularsenescence and associated inflammatory secretory phenotype is likely to identify the molecular mechanisms that contribute to the development of aging-associated human inflammatory diseases and a failure to cancer therapy. PMID:27063514

The senescence-accelerated strains of mice (SAMP) are well-characterized animal models of senescence. Senescence may be related to enhanced production or defective control of reactive oxygen species, which lead to neuronal damage. Therefore, the activity of various oxidative-stress related enzymes was determined in the cortex of 5 months-old senescence-accelerated mice prone-8 (SAMP-8) of both sexes and compared with senescence-accelerated mice-resistant-1 (SAMR-1). Glutathione reductase and peroxidase activities in SAMP-8 male mice were lower than in male SAMR-1, and a decreased catalase activity was found in both male and female SAMP-8 mice, which correlates with the lower catalase expression found by Western blotting. Nissl staining showed marked loss of neuronal cells in the cerebral cortex of five month-old SAMP-8 mice. SAMP-8 mice also had marked astrogliosis and microgliosis. We also found an increase in caspase-3 and calpain activity in the cortex. In addition, we observed morphological changes in the immunostaining of tau protein in SAMP-8, indicative of a loss of their structural function. Altogether, these results show that, at as early as 5 months of age, SAMP-8 mice have cytological and molecular alterations indicative of neurodegeneration in the cerebral cortex and suggestive of altered control of the production of oxidative species and hyper-activation of calcium-dependent enzymes. PMID:16542809

Senescence-Accelerated Mouse (SAM), a murine model of acceleratedsenescence, has been established by Takeda et al. (1981). SAM consists of senescence-accelerated-prone mouse (SAMP) and senescence-accelerated-resistant mouse (SAMR), the latter of which shows normal aging characteristics. In 1991 there were eight different substrains in the P-series, which commonly exhibited accelerated aging with a shortened life span (Takeda et al., 1991). Among the P-series, we have found that SAMP8 mice show significant impairments in a variety of learning tasks when compared with SAMR1 mice (Miyamoto et al., 1986). Further studies suggest that SAMP8 exhibits an age-related emotional disorder characterized by reduced anxiety-like behavior (Miyamoto et al., 1992). On the other hand, it has been shown that SAMP10 exhibits brain atrophy and learning impairments in an avoidance task (Shimada et al., 1992, 1993). Here, characteristics of age-related deficits in learning and memory, changes in emotional behavior, and abnormality of circadian rhythms in SAMP8 and SAMP10 mice are described. In the experiments, SAMP8/Ta (SAMP8), SAMP10/(/)Ta (SAMP10) and SAMR1TA (SAMR1) reared under specific pathogen-free conditions at Takeda Chemical Industries were used. PMID:9088911

The aim of our study was to evaluate if Sirt6, a NAD + dependent histone deacetylase, plays a protective role in cartilage degeneration by suppressing cellularsenescence and inflammatory responses. The expression level of sirt6 in normal and OA human knee articular cartilage was compared by immunofluorescence and western blotting. The effect of sirt6 overexpression on replicative senescence of chondrocytes and NF-κB target genes expression was evaluated. Histological assessment of OA mice knee joint was carried out to assess the in vivo effects of sirt6 overexpression on mice chondrocytes. We found sirt6 level was significantly decreased in the articular chondrocytes of OA patients compare to normal human. SA-β-gal staining revealed that overexpression of sirt6 suppressed replicative senescence of chondrocytes. Meanwhile, the expression of NF-κB dependent genes were significantly attenuated by sirt6 overxpression. Safranin-O staining and OARSI score of knee joint cartilage in OA mice revealed that Lenti-Sirt6 intraarticular injection could protect mice chondrocytes from degeneration. These data strongly suggest that overexpression of Sirt6 can prevent OA development by reducing both the inflammatory response and chondrocytes senescence. Therefore, the development of specific activators of Sirt6 may have therapeutic potential for the treatment of OA. PMID:26639398

Oncogene-induced senescence (OIS) is a critical tumor-suppressing mechanism that restrains cancer progression at premalignant stages, in part by causing telomere dysfunction. Currently it is unknown whether this proliferative arrest presents a stable and therefore irreversible barrier to cancer progression. Here we demonstrate that cells frequently escape OIS induced by oncogenic H-Ras and B-Raf, after a prolonged period in the senescence arrested state. Cells that had escaped senescence displayed high oncogene expression levels, retained functional DNA damage responses, and acquired chromatin changes that promoted c-Myc–dependent expression of the human telomerase reverse transcriptase gene (hTERT). Telomerase was able to resolve existing telomeric DNA damage response foci and suppressed formation of new ones that were generated as a consequence of DNA replication stress and oncogenic signals. Inhibition of MAP kinase signaling, suppressing c-Myc expression, or inhibiting telomerase activity, caused telomere dysfunction and proliferative defects in cells that had escaped senescence, whereas ectopic expression of hTERT facilitated OIS escape. In human early neoplastic skin and breast tissue, hTERT expression was detected in cells that displayed features of senescence, suggesting that reactivation of telomerase expression in senescent cells is an early event during cancer progression in humans. Together, our data demonstrate that cells arrested in OIS retain the potential to escape senescence by mechanisms that involve derepression of hTERT expression. PMID:27503890

Oncogene-induced senescence (OIS) is a critical tumor-suppressing mechanism that restrains cancer progression at premalignant stages, in part by causing telomere dysfunction. Currently it is unknown whether this proliferative arrest presents a stable and therefore irreversible barrier to cancer progression. Here we demonstrate that cells frequently escape OIS induced by oncogenic H-Ras and B-Raf, after a prolonged period in the senescence arrested state. Cells that had escaped senescence displayed high oncogene expression levels, retained functional DNA damage responses, and acquired chromatin changes that promoted c-Myc-dependent expression of the human telomerase reverse transcriptase gene (hTERT). Telomerase was able to resolve existing telomeric DNA damage response foci and suppressed formation of new ones that were generated as a consequence of DNA replication stress and oncogenic signals. Inhibition of MAP kinase signaling, suppressing c-Myc expression, or inhibiting telomerase activity, caused telomere dysfunction and proliferative defects in cells that had escaped senescence, whereas ectopic expression of hTERT facilitated OIS escape. In human early neoplastic skin and breast tissue, hTERT expression was detected in cells that displayed features of senescence, suggesting that reactivation of telomerase expression in senescent cells is an early event during cancer progression in humans. Together, our data demonstrate that cells arrested in OIS retain the potential to escape senescence by mechanisms that involve derepression of hTERT expression. PMID:27503890

The immunohistochemical localization of amyloid beta/A4 protein in the senescence-accelerated mouse brain was studied using six different antisera against human amyloid precursor protein peptides. beta/A4 proteinlike immunoreactivity was observed in the form of granular structures (beta-LIGS) in various regions, including the medial septum, cerebral cortex, hippocampus, cerebellum, and some cranial nerve roots. beta-LIGS were 1.5 to 2.5 mu in diameter and irregularly shaped. They increased significantly in number with aging, predominantly in animals with a phenotype of age-related deterioration of memory and learning abilities. Congo red and thioflavine S did not stain the granules. On immunoblots, the main immunoreactive bands were observed at 14 to 18 kd. The staining intensities of these bands also increased with advancing age. We consider that beta-LIGS are not only a new morphological manifestation of senescence in mice, but also a pertinent clue in understanding the mechanisms of amyloid deposition. Images Figure 1 Figure 3 Figure 4 PMID:8506956

The effects of orally administered sphingomyelin-based liposomes (SM-lipo) on muscle function were investigated in senescence-accelerated mice prone 1 (SAMP1) for the purpose of protection against or treatment of sarcopenia. SM-lipo were prepared by thin lipid-film hydration followed by extrusion. Their spherical shape was observed by transmission electron microscopy. The obtained liposomes were stable in gastric liquid and intestinal fluid models as well as in water. In in vitro tests liposomalization of sphingomyelin significantly increased its transport into human intestinal epithelial Caco-2 cells. In addition, SM-lipo upregulated the proliferation of murine C2C12 myoblasts compared with free sphingomyelin or phosphatidylcholine-based liposomes (PC-lipo). Finally, SM-lipo orally administered to SAMP1 for 10 weeks significantly increased quadriceps femoris weight and extended swimming time until fatigue compared with PC-lipo. In conclusion, these findings indicate that SM-lipo are well absorbed into the body and improve muscle weakness caused by senescence. PMID:27150148

In this study, we examined 3-month-old female mice from the senescence-accelerated prone mouse 8 strain and age-matched homologous normal aging female mice from the senescenceaccelerated- resistant mouse 1 strain. Mice from each strain were housed in an enriched environment (including a platform, running wheels, tunnel, and some toys) or a standard environment for 3 months. The mice housed in the enriched environment exhibited shorter escape latencies and a greater percentage of time in the target quadrant in the Morris water maze test, and they exhibited reduced errors and longer latencies in step-down avoidance experiments compared with mice housed in the standard environment. Correspondently, brain-derived neurotrophic factor mRNA and protein expression in the hippocampus was significantly higher in mice housed in the enriched environment compared with those housed in the standard environment, and the level of hippocampal brain-derived neurotrophic factor protein was positively correlated with the learning and memory abilities of mice from the senescence-accelerated prone mouse 8 strain. These results suggest that an enriched environment improved cognitive performance in mice form the senescence-accelerated prone mouse 8 strain by increasing brain-derived neurotrophic factor expression in the hippocampus. PMID:25624804

AKTIP is a shelterin-interacting protein required for replication of telomeric DNA. Here, we show that AKTIP biochemically interacts with A- and B-type lamins and affects lamin A, but not lamin C or B, expression. In interphase cells, AKTIP localizes at the nuclear rim and in discrete regions of the nucleoplasm just like lamins. Double immunostaining revealed that AKTIP partially co-localizes with lamin B1 and lamin A/C in interphase cells, and that proper AKTIP localization requires functional lamin A. In mitotic cells, AKTIP is enriched at the spindle poles and at the midbody of late telophase cells similar to lamin B1. AKTIP-depleted cells show senescence-associated markers and recapitulate several aspects of the progeroid phenotype. Collectively, our results indicate that AKTIP is a new player in lamin-related processes, including those that govern nuclear architecture, telomere homeostasis and cellularsenescence. PMID:27512140

AKTIP is a shelterin-interacting protein required for replication of telomeric DNA. Here, we show that AKTIP biochemically interacts with A- and B-type lamins and affects lamin A, but not lamin C or B, expression. In interphase cells, AKTIP localizes at the nuclear rim and in discrete regions of the nucleoplasm just like lamins. Double immunostaining revealed that AKTIP partially co-localizes with lamin B1 and lamin A/C in interphase cells, and that proper AKTIP localization requires functional lamin A. In mitotic cells, AKTIP is enriched at the spindle poles and at the midbody of late telophase cells similar to lamin B1. AKTIP-depleted cells show senescence-associated markers and recapitulate several aspects of the progeroid phenotype. Collectively, our results indicate that AKTIP is a new player in lamin-related processes, including those that govern nuclear architecture, telomere homeostasis and cellularsenescence. PMID:27512140

The environment in which organisms live can greatly influence their development. Consequently, environmental enrichment (EE) is progressively recognized as an important component in the improvement of brain function and development. It has been demonstrated that rodents raised under EE conditions exhibit favorable neuroanatomical effects that improve their learning, spatial memory, and behavioral performance. Here, by using senescence-accelerated prone mice (SAMP8) and these as a model of adverse genetic conditions for brain development, we determined the effect of EE by raising these mice during early life under favorable conditions. We found a better generalized performance of SAMP8 under EE in the results of four behavioral and learning tests. In addition, we demonstrated broad molecular correlation in the hippocampus by an increase in NeuN and Ki67 expression, as well as an increase in the expression of neurotrophic factors, such as pleiotrophin (PTN) and brain-derived neurotrophic factor (BDNF), with a parallel decrease in neurodegenerative markers such as GSK3, amyloid-beta precursor protein, and phosphorylated beta-catenin, and a reduction of SBDP120, Bax, GFAP, and interleukin-6 (IL-6), resulting in a neuroprotective panorama. Globally, it can be concluded that EE applied to SAMP8 at young ages resulted in epigenetic regulatory mechanisms that give rise to significant beneficial effects at the molecular, cellular, and behavioral levels during brain development, particularly in the hippocampus. PMID:26014386

The senescence-accelerated mouse (SAM) was developed by selective breeding of the AKR/J strain, based on a graded score for senescence, which led to the development of both senescence-accelerated prone (SAMP), and senescence-accelerated resistant (SAMR) strains. Among the SAMP strains, SAMP6 is well characterized as a model of senile osteoporosis, but its brain and neuronal functions have not been well studied. We therefore decided to characterize the central nervous system of SAMP6, in combination with different behavioral tests and analysis of its biochemical and pharmacological properties. Multiple behavioral tests revealed higher motor activity, reduced anxiety, anti-depressant activity, motor coordination deficits, and enhanced learning and memory in SAMP6 compared with SAMR1. Biochemical and pharmacological analyses revealed several alterations in the dopamine and serotonin systems, and in long-term potentiation (LTP)-related molecules. In this review, we discuss the possibility of using SAMP6 as a model of brain function. PMID:24521858

Blood stasis syndrome (BSS) is an important pathologic condition in traditional East Asian medicine, characterized by multiple signs and symptoms, including sublingual varicosis, angiotelectasis, slow and choppy pulse, local fixed pain, nyctalgia, menstrual cramps, dark-purple tongue and infra-orbital darkness. However, recent studies have been restricted to the circulatory disorder and could not suggest the pathologic core to explain all of the characteristics of BSS. Here, we review the current research on the senescence of red blood cells (RBCs), focusing on the correlation between the pathologic properties of senescent RBCs and BSS-specific manifestations. The accumulation of senescent RBCs and their products induce pathological conditions that affect blood flow resistance and cause thrombosis, vasoconstriction and methemoglobinemia. These pathological alterations are identical to the characteristics of BSS, therefore supporting the hypothesis that accelerated RBC aging could be considered as a novel pathologic mechanism of BSS. PMID:26045884

The RB protein family (RB, p107, and p130) has overlapping and compensatory functions in cell-cycle control. However, cancer-associated mutations are almost exclusively found in RB, implying that RB has a nonredundant role in tumor suppression. We demonstrate that RB preferentially associates with E2F target genes involved in DNA replication and is uniquely required to repress these genes during senescence but not other growth states. Consequently, RB loss leads to inappropriate DNA synthesis following a senescence trigger and, together with disruption of a p21-mediated cell-cycle checkpoint, enables extensive proliferation and rampant genomic instability. Our results identify a nonredundant RB effector function that may contribute to tumor suppression and reveal how loss of RB and p53 cooperate to bypass senescence. PMID:20385362

Epigenetic states can govern the plasticity of a genome to be adaptive to environments where many stress stimuli and insults compromise the homeostatic system with age. Although certain elastic power may autonomously reset, reprogram, rejuvenate, or reverse the organismal aging process, enforced genetic manipulations could at least reset and reprogram epigenetic states beyond phenotypic plasticity and elasticity in cells, which can be further manipulated into organisms. The question, however, remains how we can rejuvenate intrinsic resources and infrastructures in a noninvasive manner, particularly in a whole complex aging organism. Given inevitable increase of cancer with age, presumably any failure of resetting, reprogramming, or even rejuvenation could be a prominent causative factor of malignancy. Accompanied by progressive deteriorations of physiological functions in organisms with advancing age, aging-associated cancer risk may essentially arise from unforeseen complications in cellularsenescence. At the cellular level, epithelial-mesenchymal plasticity (dynamic and reversible transitions between epithelial and mesenchymal phenotypic states) is enabled by underlying shifts in epigenetic regulation. Thus, the epithelial-mesenchymal transition (EMT) and its reversal (mesenchymal-epithelial transition [MET]) function as a key of cellular transdifferentiation programs. On the one hand, the EMT-MET process was initially appreciated in developmental biology, but is now attracting increasing attention in oncogenesis and senescence, because the process is involved in the malignant progression vs regression of cancer. On the other hand, senescence is often considered the antithesis of early development, but yet between these 2 phenomena, there may be common factors and governing mechanisms such as the EMT-MET program, to steer toward rejuvenation of the biological aging system, thereby precisely controlling or avoiding cancer through epigenetic interventions. PMID

Most studies on cellularsenescence (CS) have been performed in vitro by employing cytotoxic agents, irradiation, chromatin and telomerase modulators or by activating certain oncogenes. All these approaches usually lead to DNA damage, gene instability and/or chromatin alterations that primarily affect p53-p21 signaling. Little is known on whether retinoids and rexinoids, which are cell differentiation agents, can also induce CS in vitro and in vivo, and which molecular mechanisms are involved in promoting the senescent phenotype. We reviewed the recent publications on CS induced by retinoids and rexinoids in ER+ and ER− breast cancer cell lines and in corresponding animal models of mammary carcinogenesis which simulate those of human breast cancer. The role of retinoic acid receptors β2 and 5 (RARβ2 and RARβ5) and of receptor independent genes involved in mediating the senescence program of retinoids and rexinoids in ER+ and ER− breast cancer cells is discussed. Potential strategists for clinical implication of CS as biomarker of prognosis and of response to treatment with retinoids, rexinoids and with other cell differentiation and antitumor agents are outlined. PMID:25997921

Genome instability triggers cellularsenescence and is a common cause of cancer. The ribosomal RNA genes (rDNA), due to their repetitive structure, form a fragile site with frequent rearrangements. To identify eukaryotic factors that connect reduced genome stability to senescence we screened 4,876 strains of a Saccharomyces cerevisiae deletion library for aberrant rDNA and found 708 genes that contribute to its upkeep. 28 mutants caused abnormalities in non-rDNA chromosomes and among them 12 mutants have abnormalities both in rDNA and in non-rDNA chromosomes. Many mutated genes have not previously been implicated with genome maintenance nor their homologues with tumorigenesis in mammals. The link between rDNA state and senescence was broken after deletion of factors related with DNA polymerase ϵ. These mutations also suppressed the short lifespan phenotype of a sir2 mutant, suggesting a model in which molecular events at the heart of the replication fork induce abnormal rDNA recombination and are responsible for the emergence of an aging signal. PMID:26912831

Dental pulp stem cells (DPSCs) are a type of mesenchymal stem cell (MSC) characterized by multi-lineage differentiation making it an attractive choice for tissue regeneration. However, before DPSCs can be used for cell-based therapy, we have to understand their biological properties in response to intrinsic and extrinsic stimuli such as lipopolysaccharide (LPS). DPSCs were therefore stimulated with LPS and senescence was evaluated by senescence-associated β-galactosidase (SA-β-gal) staining, with cell number and cell-cycle arrest being examined by BrdU assay and flow cytometry, respectively. The morphology of DPSCs was characterized by their flat shape, increased size and increased SA-β-gal activity after repeated stimulation (3 or 6 times) with LPS. Reactive oxygen species (ROS) staining showed that the number of ROS-stained cells and the DCFH fluorescent level were higher in the LPS-treated DPSCs compared with those in the untreated DPSCs. Protein and mRNA expression levels of γ-H2A.X and p16(INK4A) were also increased in DPSCs with repeated LPS stimulation. We found that the LPS bound with Toll-like receptor 4 (TLR4) and that TLR4 signaling accounted for p16(INK4A) expression. Further results indicated that the senescence of DPSCs stimulated repeatedly with LPS was reversed by p16(INK4A) short interfering RNA. The DNA damage response and p16(INK4A) pathways might be the main mediators of DPSC senescence induced by repeated LPS stimulation. Thus, DPSCs tend to undergo senescence after repeated activation, implying that DPSC senescence starts after many inflammatory challenges. Ultimately, these findings should lead to a better understanding of DPSC-based clinical therapy. PMID:24676500

Endogenous retroelements (ERs) represent nearly half of the human genome. Considered up to recent years as "functionless" DNA sequences, they are now known to be involved in important cellular functions such as stress response and generation of non coding regulatory RNAs. Moreover, an increasing amount of data supports the idea of ERs as key players in cellularsenescence and in different senescence-related pathogenic cellular processes, including those leading to inflammation, cancer and major age-related multifactorial diseases. The involvement of ERs in these biological mechanisms can suggest new therapeutic strategies in neoplasms, inflammatory/autoimmune diseases and in different age-related pathologies, such as macular degeneration, diabetes, cardiovascular diseases and major age-related neurodegenerative disorders. The therapeutic approaches which can be suggested range from a set of well-known, common drugs that have been shown to modulate ERs activity, to immune therapy against ER-derived tumor antigens, to more challenging strategies such as those based on anti-ERs RNA interference. PMID:25981608

Heat stress is one of the best-studied cellular stress factors; however, little is known about its delayed effects. Here, we demonstrate that heat stress induces p21-dependent cellularsenescence-like cell cycle arrest. Notably, only early S-phase cells undergo such an arrest in response to heat stress. The encounter of DNA replication forks with topoisomerase I-generated single-stranded DNA breaks resulted in the generation of persistent double-stranded DNA breaks was found to be a primary cause of heat stress-induced cellularsenescence in these cells. This investigation of heat stress-induced cellularsenescence elucidates the mechanisms underlying the exclusive sensitivity of early S-phase cells to ultra-low doses of agents that induce single-stranded DNA breaks. PMID:26032771

Senescence-accelerated mouse (SAM) is an experimental model animal showing a short lifespan and rapid advancement of senescence. Especially, SAM prone 8 (SAMP8) shows age-related impairment of learning and memory, and thus, it is a good model for age-related cognitive function. However, the synaptic characteristics related to cognitive function of SAMP8 have been poorly understood. In this study, we quantitatively evaluated the synaptic transmission and synaptic plasticity using hippocampal slices obtained from SAMP8 with electrophysiological methods to elucidate the synaptic features of SAMP8. We used the field recordings to measure some synaptic parameters. The slope of field excitatory postsynaptic potentials decreased with age in both SAMP8 and SAM resistant 1 (SAMR1), the control strain of SAMP8. The paired-pulse ratio (PPR), a representative of short-term synaptic plasticity, also decreased in both strains with age. On the other hand, although both SAMR1 and SAMP8 exhibited age-dependent decrease in long-term potentiation (LTP), a representative of long-term synaptic plasticity, the decrease in LTP in SAMP8 started at 6 months of age, while in SAMR1, it was observed at 14 months but not at 6 months of age. The PPRs after high-frequency stimulation for LTP induction were smaller than those before the stimulation. These results indicate that synaptic plasticity in SAMP8 deteriorates at an earlier age compared to SAMR1, and are consistent with behavioral tests showing early impairment of learning and memory of SAMP8. Our study is the first report on quantitative analysis of synaptic function at SAMP8 hippocampus and corroborates the behavioral studies showing cognitive dysfunction with age; therefore, it will be helpful for future studies on aging. PMID:26195169

MicroRNAs (miRNAs) have emerged as important regulators of tumorigenesis. Several miRNAs, which can function either as oncomiRs or tumor suppressive miRs are deregulated in cancer cells. The microRNA-31 (miR-31) has been shown to be overexpressed in metastatic breast cancer. It promotes multiple oncogenic phenotypes, including proliferation, motility, and invasion of cancer cells. Using a breast cancer-related miRNA array analysis, we identified miR-31 as a novel target of histone deacetylase inhibitors (HDACi) in breast cancer cells. Specifically, we show that sodium butyrate (NaB) and panobinostat (LBH589), two broad-spectrum HDAC inhibitors up-regulate hsa-miR-31 (miR-31). The up-regulation of miR-31 was accompanied by repression of the polycomb group (PcG) protein BMI1 and induction of cellularsenescence. We further show that inhibition of miR-31 overcomes the senescence-inducing effect of HDACi, and restores expression of the PcG protein BMI1. Interestingly, BMI1 also acts as a repressor of miR-31 transcription, suggesting a cross-negative feedback loop between the expression of miR-31 and BMI1. Our data suggest that miR-31 is an important physiological target of HDACi, and that it is an important regulator of senescence relevant to cancer. These studies further suggest that manipulation of miR-31 expression can be used to modulate senescence-related pathological conditions such as cancer, and the aging process. PMID:25737447

MicroRNAs (miRNAs) have emerged as important regulators of tumorigenesis. Several miRNAs, which can function either as oncomiRs or tumor suppressive miRs are deregulated in cancer cells. The microRNA-31 (miR-31) has been shown to be overexpressed in metastatic breast cancer. It promotes multiple oncogenic phenotypes, including proliferation, motility, and invasion of cancer cells. Using a breast cancer-related miRNA array analysis, we identified miR-31 as a novel target of histone deacetylase inhibitors (HDACi) in breast cancer cells. Specifically, we show that sodium butyrate (NaB) and panobinostat (LBH589), two broad-spectrum HDAC inhibitors up-regulate hsa-miR-31 (miR-31). The up-regulation of miR-31 was accompanied by repression of the polycomb group (PcG) protein BMI1 and induction of cellularsenescence. We further show that inhibition of miR-31 overcomes the senescence-inducing effect of HDACi, and restores expression of the PcG protein BMI1. Interestingly, BMI1 also acts as a repressor of miR-31 transcription, suggesting a cross-negative feedback loop between the expression of miR-31 and BMI1. Our data suggest that miR-31 is an important physiological target of HDACi, and that it is an important regulator of senescence relevant to cancer. These studies further suggest that manipulation of miR-31 expression can be used to modulate senescence-related pathological conditions such as cancer, and the aging process. PMID:25737447

The SAM strains, a group of related inbred strains consisting of senescence-prone inbred strains (SAMP) and senescence-resistant inbred strains (SAMR), have been successfully developed by selective inbreeding of the AKR/J strain of mice donated by the Jackson laboratory in 1968. The characteristic feature of aging common to the SAMP and SAMR is acceleratedsenescence and normal aging, respectively. Furthermore, SAMP and SAMR strains of mice manifest various pathobiological phenotypes spontaneously. Among SAMP strains, SAMP8 and SAMP10 mice show age-related behavioral deterioration such as deficits in learning and memory, emotional disorders (reduced anxiety-like behavior and depressive behavior) and altered circadian rhythm associated with certain pathological, biochemical and pharmacological changes. Here, the previous and recent literature on SAM mice are reviewed with an emphasis on SAMP8 and SAMP10 mice. A spontaneous model like SAM with distinct advantages over the gene-modified model is hoped by investigators to be used more widely as a biogerontological resource to explore the etiopathogenesis of acceleratedsenescence and neurodegenerative disorders. PMID:19199030

The limited effectiveness of therapy for patients with advanced stage head and neck squamous cell carcinoma (HNSCC) or recurrent disease is a reflection of an incomplete understanding of the molecular basis of HNSCC pathogenesis. MUC4, a high molecular weight glycoprotein, is differentially overexpressed in many human cancers and implicated in cancer progression and resistance to several chemotherapies. However, its clinical relevance and the molecular mechanisms through which it mediates HNSCC progression are not well understood. This study revealed a significant upregulation of MUC4 in 78% (68/87) of HNSCC tissues compared with 10% positivity (1/10) in benign samples (P=0.006, odds ratio (95% confidence interval)=10.74 (2.0-57.56). MUC4 knockdown (KD) in SCC1 and SCC10B HNSCC cell lines resulted in significant inhibition of growth in vitro and in vivo, increased senescence as indicated by an increase in the number of flat, enlarged and senescence-associated β-galactosidase (SA-β-Gal)-positive cells. Decreased cellular proliferation was associated with G0/G1 cell cycle arrest and decrease expression of cell cycle regulatory proteins like cyclin E, cyclin D1 and decrease in BrdU incorporation. Mechanistic studies revealed upregulation of p16, pRb dephosphorylation and its interaction with histone deacetylase 1/2. This resulted in decreased histone acetylation (H3K9) at cyclin E promoter leading to its downregulation. Orthotopic implantation of MUC4 KD SCC1 cells into the floor of the mouth in nude mice resulted in the formation of significantly smaller tumors (170±18.30 mg) compared to those (375±17.29 mg) formed by control cells (P=0.00007). In conclusion, our findings showed that MUC4 overexpression has a critical role by regulating proliferation and cellularsenescence of HNSCC cells. Downregulation of MUC4 may be a promising therapeutic approach for treating HNSCC patients. PMID:24747969

Senescence-accelerated mice (SAM P8 and R1) were behaviorally assessed in a cross-sectional study at 4 and 15 months of age. Behavioral measures included memory (place discrimination and repeated acquisition in a water maze), sensorimotor performance (turning in an alley, traversing bridges, wire rod hanging, and falls from a wire screen), psychomotor performance (open-field exploration), and emotionality (entries in a plus maze, grooming, and defecation in a plus maze and in an open field). In the water maze, aged P8 mice were impaired in place discrimination and in repeated acquisition tasks, demonstrating evidence of an age-related decline in spatial memory processing abilities. The demonstration of this impairment, however, was complicated by noncognitive factors, such as the tendency of many older P8 mice to float. Sensorimotor skill impairment was accelerated with age in P8 mice, but not in R1 mice, and this impairment was present despite the lack of age-related changes in body weight in P8 mice. Although P8 and R1 mice were not different in general activity at old age, P8 mice were substantially more hyperactive in an open field and in the plus maze than R1 mice when compared at young age. Independent of age, P8 mice demonstrated a reduction of anxiety-like behavior in the plus maze. Taken as a whole, the data suggest that although age-related behavioral alterations occur in the P8 mice, some of these changes are evident at 4 months of age. Thus, the behavioral abnormalities that exist not only represent an accelerated aging phenomenon but may also be considered a developmental pathology. PMID:9661977

Sarcopenia is an age-related systemic syndrome with progressive deterioration in skeletal muscle functions and loss in mass. Although the senescence-accelerated mouse P8 (SAMP8) was reported valid for muscular ageing research, there was no report on the details such as sarcopenia onset time. Therefore, this study was to investigate the change of muscle mass, structure and functions during the development of sarcopenia. Besides the average life span, muscle mass, structural and functional measurements were also studied. Male SAMP8 animals were examined at month 6, 7, 8, 9, and 10, in which the right gastrocnemius was isolated and tested for ex vivo contractile properties and fatigability while the contralateral one was harvested for muscle fiber cross-sectional area (FCSA) and typing assessments. Results showed that the peak of muscle mass appeared at month 7 and the onset of contractility decline was observed from month 8. Compared with month 8, most of the functional parameters at month 10 decreased significantly. Structurally, muscle fiber type IIA made up the largest proportion of the gastrocnemius, and the fiber size was found to peak at month 8. Based on the altered muscle mass, structural and functional outcomes, it was concluded that the onset of sarcopenia in SAMP8 animals was at month 8. SAMP8 animals at month 8 should be at pre-sarcopenia stage while month 10 at sarcopenia stage. It is confirmed that SAMP8 mouse can be used in sarcopenia research with established time line in this study. PMID:26193895

Senescenceaccelerated mice (SAM) are a group of mice that show aging-related diseases, and SAM prone 10 (SAMP10) show spontaneous brain atrophy and defects in learning and memory. Our previous report showed that the thymus and the percentage of T lymphocytes are abnormal in the SAMP10, but it was unclear whether the bone marrow-derived mesenchymal stroma cells (BMMSCs) were abnormal, and whether they played an important role in regenerative medicine. We thus compared BMMSCs from SAMP10 and their control, SAM-resistant (SAMR1), in terms of cell cycle, oxidative stress, and the expression of PI3K and mitogen-activated protein kinase (MAPK). Our cell cycle analysis showed that cell cycle arrest occurred in the G0/G1 phase in the SAMP10. We also found increased reactive oxygen stress and decreased PI3K and MAPK on the BMMSCs. These results suggested the BMMSCs were abnormal in SAMP10, and that this might be related to the immune system dysfunction in these mice. PMID:26840301

Senescence-accelerated mouse (SAM) is inbred lines of mice originally developed from AKR/J mice. Among the six SAM prone (SAMP) substrains, 8- to 12-month-old SAMP8 have long been used as a model of age-related cognitive impairments. However, little is still known for younger SAMP8 mice. Here, we examined the phenotypical characteristics of 4-month-old SAMP8 using a battery of behavioral tests. Four-month-old SAMP8 mice failed to recognize spatially displaced object in an object recognition task and performed poorly in the probe test of the Morris water maze task compared to SAMR1, suggesting that SAMP8 have impaired spatial memory. In addition, young SAMP8 exhibited enhanced anxiety-like behavior in an open field test and showed depression-like behavior in the forced-swim test. Their circadian rhythm was also disrupted. These abnormal behaviors of young SAMP8 are similar to behavioral alterations also observed in aged mice. In summary, age-related behavioral alterations occur in SAMP8 as young as 4 months old. PMID:27093926

Osteoporosis is a major disease associated with aging. We have previously demonstrated that diosgenin prevents osteoporosis in both menopause and D-galactose-induced aging rats. OXYS rats reveal an acceleratedsenescence and are used as a suitable model of osteoporosis. The aim of the present study was to analyze microarchitecture and morphological changes in femur of OXYS rats using morphological tests and microcomputed tomography scanning, and to evaluate the effects of oral administration of diosgenin at 10 and 50 mg/kg/day on femur in OXYS rats. The result showed that, compared with age-matched Wistar rats, the femur of OXYS rats revealed lower bone length, bone weight, bone volume, frame volume, frame density, void volume, porosity, external and internal diameters, cortical bone area, BV/TV, Tb.N, and Tb.Th, but higher Tb.Sp. Eight weeks of diosgenin treatment decreased porosity and Tb.Sp, but increased BV/TV, cortical bone area, Tb.N and bone mineral density, compared with OXYS rats treated with vehicle. These data reveal that microarchitecture and morphological changes in femur of OXYS rats showed osteoporotic aging features and suggest that diosgenin may have beneficial effects on aging-induced osteoporosis. PMID:26387656

Although muscle wasting and/or degeneration are prevalent in patients with chronic kidney disease, it remains unknown whether FGF-23 influences muscle homeostasis and regeneration. Mesenchymal stem cells (MSCs) in skeletal muscle are distinct from satellite cells and have a known association with muscle degeneration. In this study we sought to investigate the effects of FGF-23 on MSCs isolated from human skeletal muscle in vitro. The MSCs expressed FGF receptors (1 through 4) and angiotensin-II type 1 receptor, but no traces of the Klotho gene were detected. MSCs and satellite cells were treated with FGF-23 and angiotensin-II for 48 h. Treatment with FGF-23 significantly decreased the number of MSCs compared to controls, while treatment with angiotensin-II did not. FGF-23 and angiotensin-II both left the cell counts of the satellite cells unchanged. The FGF-23-treated MSCs exhibited the senescent phenotype, as judged by senescence-associated β-galactosidase assay, cell morphology, and increased expression of p53 and p21 in western blot analysis. FGF-23 also significantly altered the gene expression of oxidative stress regulators in the cells. In conclusion, FGF-23 induced premature senescence in MSCs from skeletal muscle via the p53/p21/oxidative-stress pathway. The interaction between the MSCs and FGF-23 may play a key role in the impaired muscle reparative mechanisms of chronic kidney disease. PMID:26797283

Female senescenceaccelerated mice SAMP-1. (prone) and SAMR-1 (resistant) were exposed 5 times a week monthly to melatonin (with drinking water 20mg/ml during the night hours) or to s.c. injections of epitalon (Ala-Glu-Asp-Gly) at a single dose 1mkg/mouse. Control mice were intact or exposed to injection of 0.1 ml normal saline. The body weight and temperature, food consumption, estrous function were monitored regularly. The life span and tumor incidence were evaluated as well. As age advanced, the weight increased whereas food consumption and body temperature did not change. There was no significant substrain difference in these parameters. Exposure to melatonin or epitalon also failed to influence those indices. As age advanced, the incidence of irregular estrous cycles increased both in SAMP-1 and SAMR-1, whereas the treatment with both melatonin and epitalon prevented such disturbances. SAMP-1 revealed some features of accelerated aging as compared to SAMR-1. The mean life span of the 10% of the last survivors among treated SAMP-1 was shorter than that of SAMR-1, aging rate increased and mortality doubling time decreased. There was a direct correlation between body mass of the two substrains at the age of 3 and 12 months matched by body mass increase and longer life span. Melatonin or epitalon treatment was followed by longer mean and maximum survival in the 10% of the last survivors among SAMP-1. Melatonin involved decreased aging rate and increased mortality doubling time. Malignant lymphomas predominated in SAM without any significant difference in frequency between the substrains. While melatonin failed to influence tumor incidence or term of detection in SAMP-1, neither did epitalon affect frequency. However, it was followed by longer survival in tumor-free animals. No link between melatonin or epitalon treatment, on the one hand, and carcinogenesis, on the other, was reported in SAMR-1. PMID:15909815

Petal development and senescence entails a normally irreversible process. It starts with petal expansion and pigment production, and ends with nutrient remobilization and ultimately cell death. In many species this is accompanied by petal abscission. Post-harvest stress is an important factor in limiting petal longevity in cut flowers and accelerates some of the processes of senescence such as petal wilting and abscission. However, some of the effects of moderate stress in young flowers are reversible with appropriate treatments. Transcriptomic studies have shown that distinct gene sets are expressed during petal development and senescence. Despite this, the overlap in gene expression between developmental and stress-induced senescence in petals has not been fully investigated in any species. Here a custom-made cDNA microarray from Alstroemeria petals was used to investigate the overlap in gene expression between developmental changes (bud to first sign of senescence) and typical post-harvest stress treatments. Young flowers were stressed by cold or ambient temperatures without water followed by a recovery and rehydration period. Stressed flowers were still at the bud stage after stress treatments. Microarray analysis showed that ambient dehydration stress accelerates many of the changes in gene expression patterns that would normally occur during developmental senescence. However, a higher proportion of gene expression changes in response to cold stress were specific to this stimulus and not senescence related. The expression of 21 transcription factors was characterized, showing that overlapping sets of regulatory genes are activated during developmental senescence and by different stresses. PMID:20457576

Petal development and senescence entails a normally irreversible process. It starts with petal expansion and pigment production, and ends with nutrient remobilization and ultimately cell death. In many species this is accompanied by petal abscission. Post-harvest stress is an important factor in limiting petal longevity in cut flowers and accelerates some of the processes of senescence such as petal wilting and abscission. However, some of the effects of moderate stress in young flowers are reversible with appropriate treatments. Transcriptomic studies have shown that distinct gene sets are expressed during petal development and senescence. Despite this, the overlap in gene expression between developmental and stress-induced senescence in petals has not been fully investigated in any species. Here a custom-made cDNA microarray from Alstroemeria petals was used to investigate the overlap in gene expression between developmental changes (bud to first sign of senescence) and typical post-harvest stress treatments. Young flowers were stressed by cold or ambient temperatures without water followed by a recovery and rehydration period. Stressed flowers were still at the bud stage after stress treatments. Microarray analysis showed that ambient dehydration stress accelerates many of the changes in gene expression patterns that would normally occur during developmental senescence. However, a higher proportion of gene expression changes in response to cold stress were specific to this stimulus and not senescence related. The expression of 21 transcription factors was characterized, showing that overlapping sets of regulatory genes are activated during developmental senescence and by different stresses. PMID:20457576

Methylene blue (MB) delays cellularsenescence, induces complex-IV, and activates Keap1/Nrf2; however, the molecular link of these effects to MB is unclear. Since MB is redox-active, we investigated its effect on the NAD/NADH ratio in IMR90 cells. The transient increase in NAD/NADH observed in MB-treated cells triggered an investigation of the energy regulator AMPK. MB induced AMPK phosphorylation in a transient pattern, which was followed by the induction of PGC1α and SURF1: both are inducers of mitochondrial and complex-IV biogenesis. Subsequently MB-treated cells exhibited >100% increase in complex-IV activity and a 28% decline in cellular oxidants. The telomeres erosion rate was also significantly lower in MB-treated cells. A previous research suggested that the pattern of AMPK activation (i.e., chronic or transient) determines the AMPK effect on cell senescence. We identified that the anti-senescence activity of MB (transient activator) was 8-times higher than that of AICAR (chronic activator). Since MB lacked an effect on cell cycle, an MB-dependent change to cell cycle is unlikely to contribute to the anti-senescence activity. The current findings in conjunction with the activation of Keap1/Nrf2 suggest a synchronized activation of the energy and cellular defense pathways as a possible key factor in MB's potent anti-senescence activity. PMID:26386875

Hericium erinaceum is an edible and medicinal mushroom widely used in Korea, Japan, and China. On the search for biologically active compounds supporting the medicinal usage, the MeOH extract of the fruiting bodies of H. erinaceum was investigated for its chemical constituents. Six compounds were isolated and identified as hericenone D (1), (22E,24R)-5α,8α-epidioxyergosta-6,22-dien-3β-ol (2), erinacerin B (3), hericenone E (4), hericenone F (5) and isohericerin (6) by comparing their spectroscopic data with previously reported values. The inhibitory effects on adriamycin-induced cellularsenescence in human dermal fibroblasts (HDFs) and human umbilical vein endothelial cells (HUVECs) of the isolates (1-6) were studied. Among the isolated compounds, ergosterol peroxide (2) reduced senescence associated β-galactosidase (SA-β-gal) activity increased in HUVECs treated with adriamycin. According to experimental data obtained, the active compound may inspire the development of a new pharmacologically useful substance to be used in the treatment and prevention of age-related diseases. PMID:25676326

The tissue concentration of lipid peroxides was determined in the brain, heart, liver, lung and kidney of acceleratedsenescence-prone (SAMP-8) and -resistant (SAMR-1) mice at 3, 6 and 9 months of age by a method involving chemical derivatization and high performance liquid chromatography. The level of lipid peroxides in the brain did not show an age-dependent change, but at each age the brain level of lipid peroxides was significantly higher in SAMP-8 than in SAMR-1. In contrast, the lipid peroxide levels in the peripheral organs showed increases with aging in both strains, and they were significantly higher in SAMP-8 than in SAMR-1 at both 3 and 6 months of age (except at 3 months of age in the kidney). These results suggest that increased oxidative stress in the brain and peripheral organs is a cause of the senescence-related degeneration and impairments seen in SAMP-8. PMID:10643812

The RON receptor tyrosine kinase is a member of the MET proto-oncogene family and is important for cell proliferation, differentiation, and cancer development. Here, we created a series of Madin-Darby canine kidney (MDCK) epithelial cell clones that express different levels of RON, and have investigated their biological properties. While low levels of RON correlated with little morphological change in MDCK cells, high levels of RON expression constitutively led to morphological scattering or complete and stabilized epithelial-to-mesenchymal transition (EMT). Unexpectedly, MDCK clones expressing higher levels of RON exhibited retarded proliferation and senescence, despite increased motility and invasiveness. RON was constitutively tyrosine-phosphorylated in MDCK cells expressing high levels of RON and undergoing EMT, and the MAPK signaling pathway was activated. This study reveals for the first time that RON alone is sufficient to induce complete and stabilized EMT in MDCK cells, and overexpression of RON does not cause cell transformation but rather induces cell cycle arrest and senescence, leading to impaired cell proliferation.

Diploid cells undergoing senescence and mitotic slippage have been reported in the literature. However, the mechanisms triggering senescence in long-term G2-arrested cells are currently unclear. Previously, we reported that the cell cycle of the human uveal melanoma cell line, 92-1, is suspended for up to 6 d upon exposure to 10 Gy ionizing radiation (IR), followed by senescence. In the current study, we initially distinguished senescence in long-term blocked 92-1 cells from mitotic slippage by confirming the blockage of cells in the G2 phase. We subsequently showed that the genes essential for G2-M transition are prematurely downregulated at both the transcriptional and translational levels. Furthermore, levels of the G1-specific markers, Cyclin D1 and Caveolin-1, were distinctly increased, while S/G2-specific markers, Cyclin B1 and Aurora A, were significantly downregulated. These findings collectively imply that long-term G2-arrested cells undergo senescence via G2 slippage. To our knowledge, this is the first study to report that the cellular process of G2 slippage is the mechanism responsible for senescence of cells under long-term G2 arrest. PMID:23574719

Learning and memory are known to be influenced by circulating sex steroidal hormones and these behavioral processes are diminished in aging. Thus, the aim of this study was to examine the mechanism underlying testosterone-induced effects on cognitive performance in the senescenceaccelerated mouse P8 (SAMP8) model. Treatment with testosterone (T) as evidenced by the Morris water maze test produced a significantly shorter escape latency and reduced path length to reach the platform compared to the control (C). No significant differences were noted in mean swim speed among all groups. During the probe trials, the T group spent a significantly greater percent of time in the target quadrant and improved the number of platform crossings. Flutamide (F), an antiandrogen, significantly inhibited the effects of T on behavioral and memory performances indicators. Following Nissl staining, the number of intact pyramidal cells was markedly elevated in the treated mice, and this effect was blocked by F. Immunohistochemistry and Western blot analysis showed that the expression levels of NMDAR1, SYN, and p-CREC/CREB protein levels were significantly increased in the T group, while F inhibited the T-mediated effects. Western blot analysis showed that there were no significant differences in the expression levels of SYN, p-CREC/CREB, and NMDAR1 between C, F, and F + T groups. Reverse-transcription polymerase chain reaction (RT-PCR) analysis showed that the mRNA expression levels of NMDAR1 and SYN were significantly increased in T-administered mice, while F inhibited the T-mediated effects. Data suggest that the T-mediated increase in SYN expression levels resulted in improvement in behavioral performances and learning, which may involve stimulation of central nervous system androgen receptors (AR). PMID:26529502

Cardiac senescence and age-related disease development have gained general attention and recognition in the past decades due to increased accessibility and quality of health care. The advancement in global civilization is complementary to concerns regarding population aging and development of chronic degenerative diseases. Cardiac degeneration has been rigorously studied. The molecular mechanisms of cardiac senescence are on multiple cellular levels and hold a multilayer complexity level, thereby hampering development of unambiguous treatment protocols. In particular, the synergistic exchange of the senescence phenotype through a senescence secretome between myocytes and stem cells appears complicated and is of great future therapeutic value. The current review article will highlight hallmarks of senescence, cardiac myocyte and stem cell senescence, and the mutual exchange of senescent secretome. Future cardiac cell therapy approaches require a comprehensive understanding of myocardial senescence to improve therapeutic efficiency as well as efficacy. PMID:24349878

Cardiac senescence and age-related disease development have gained general attention and recognition in the past decades due to increased accessibility and quality of health care. The advancement in global civilization is complementary to concerns regarding population aging and development of chronic degenerative diseases. Cardiac degeneration has been rigorously studied. The molecular mechanisms of cardiac senescence are on multiple cellular levels and hold a multilayer complexity level, thereby hampering development of unambiguous treatment protocols. In particular, the synergistic exchange of the senescence phenotype through a senescence secretome between myocytes and stem cells appears complicated and is of great future therapeutic value. The current review article will highlight hallmarks of senescence, cardiac myocyte and stem cell senescence, and the mutual exchange of senescent secretome. Future cardiac cell therapy approaches require a comprehensive understanding of myocardial senescence to improve therapeutic efficiency as well as efficacy. PMID:24349878

Background and purpose We reviewed the current state of research on microRNAs in age-related diseases in cartilage and bone. Methods PubMed searches were conducted using separate terms to retrieve articles on (1) the role of microRNAs on aging and tissue degeneration, (2) specific microRNAs that influence cellular and organism senescence, (3) microRNAs in age-related musculoskeletal conditions, and (4) the diagnostic and therapeutic potential of microRNAs in age-related musculoskeletal conditions. Results An increasing number of studies have identified microRNAs associated with cellular aging and tissue degeneration. Specifically in regard to frailty, microRNAs have been found to influence the onset and course of age-related musculoskeletal conditions such as osteoporosis, osteoarthritis, and posttraumatic arthritis. Both intracellular and extracellular microRNAs may be suitable to function as diagnostic biomarkers. In particular Interpretation The research data currently available suggest that microRNAs play an important role in orchestrating age-related processes and conditions of the musculoskeletal system. Further research may help to improve our understanding of the complexity of these processes at the cellular and extracellular level. The option to develop microRNA biomarkers and novel therapeutic agents for the degenerating diseases of bone and cartilage appears to be promising. PMID:25175665

Increased levels of oxidized proteins with aging have been considered a cardiovascular risk factor. However, it is unclear whether oxidized albumin, which is the most abundant serum protein, induces endothelial damage. The results of this study indicated that with aging processes, the levels of oxidized proteins as well as endothelial microparticles release increased, a novel marker of endothelial damage. Among these, oxidized albumin seems to play a principal role. Through in vitro studies, endothelial cells cultured with oxidized albumin exhibited an increment of endothelial damage markers such as adhesion molecules and apoptosis levels. In addition, albumin oxidation increased the amount of endothelial microparticles that were released. Moreover, endothelial cells with increased oxidative stress undergo senescence. In addition, endothelial cells cultured with oxidized albumin shown a reduction in endothelial cell migration measured by wound healing. As a result, we provide the first evidence that oxidized albumin induces endothelial injury which then contributes to the increase of cardiovascular disease in the elderly subjects. PMID:27042026

Photobiomodulation (PBM) is an effect oflow intensity monochromatic light or laser irradiation (LIL) on biological systems. which stimulates or inhibits biological functions but does not result in irreducible damage. It has been observed that PBM can suppress cellularsenescence, reverse skin photoageing and improve fibromyalgia. In this paper, the biological information model of photobiomodulation (BIMP) is used to discuss its mechanism. Cellularsenescence can result from short, dysfunctional telomeres, oxidative stress, or oncogene expression, and may contribute to aging so that it can be seen as a decline of cellular function in which cAMP plays an important role, which provide a foundation for PBM on senescence since cellularsenescence is a reasonable model of senescence and PBM is a cellular rehabilitation in which cAMP also plays an important role according to BIMP. The PBM in reversing skin photoageing and improving fibromyalgia are then discussed in detail.

Litchi is a non-climacteric subtropical fruit of high commercial value. The shelf life of litchi fruit under ambient conditions (AC) is approximately 4-6 days. Post-harvest cold storage prolongs the life of litchi fruit for up to 30 days with few changes in pericarp browning and total soluble solids. However, the shelf life of litchi fruits at ambient temperatures after pre-cold storage (PCS) is only 1-2 days. To better understand the mechanisms involved in the rapid fruit senescence induced by pre-cold storage, a transcriptome of litchi pericarp was constructed to assemble the reference genes, followed by comparative transcriptomic and metabolomic analyses. Results suggested that the senescence of harvested litchi fruit was likely to be an oxidative process initiated by ABA, including oxidation of lipids, polyphenols and anthocyanins. After cold storage, PCS fruit exhibited energy deficiency, and respiratory burst was elicited through aerobic and anaerobic respiration, which was regulated specifically by an up-regulated calcium signal, G-protein-coupled receptor signalling pathway and small GTPase-mediated signal transduction. The respiratory burst was largely associated with increased production of reactive oxygen species, up-regulated peroxidase activity and initiation of the lipoxygenase pathway, which were closely related to the acceleratedsenescence of PCS fruit. PMID:26763309

Litchi is a non-climacteric subtropical fruit of high commercial value. The shelf life of litchi fruit under ambient conditions (AC) is approximately 4–6 days. Post-harvest cold storage prolongs the life of litchi fruit for up to 30 days with few changes in pericarp browning and total soluble solids. However, the shelf life of litchi fruits at ambient temperatures after pre-cold storage (PCS) is only 1–2 days. To better understand the mechanisms involved in the rapid fruit senescence induced by pre-cold storage, a transcriptome of litchi pericarp was constructed to assemble the reference genes, followed by comparative transcriptomic and metabolomic analyses. Results suggested that the senescence of harvested litchi fruit was likely to be an oxidative process initiated by ABA, including oxidation of lipids, polyphenols and anthocyanins. After cold storage, PCS fruit exhibited energy deficiency, and respiratory burst was elicited through aerobic and anaerobic respiration, which was regulated specifically by an up-regulated calcium signal, G-protein-coupled receptor signalling pathway and small GTPase-mediated signal transduction. The respiratory burst was largely associated with increased production of reactive oxygen species, up-regulated peroxidase activity and initiation of the lipoxygenase pathway, which were closely related to the acceleratedsenescence of PCS fruit. PMID:26763309

Increasing evidence suggests that miRNAs can act as either tumor suppressors or oncogenes in carcinogenesis. In the present study, we identified the role of miR-34a in regulating telomerase activity, with subsequent effect on cellularsenescence and viability. We found the higher expression of miR-34a was significantly correlated with the advanced clinicopathologic parameters in hepatocellular carcinoma. Furthermore, tumor tissues of 75 HCC patients demonstrated an inverse correlation between the miR-34a level and telomere indices (telomere length and telomerase activity). Transient introduction of miR-34a into HCC cell lines inhibited the telomerase activity and telomere length, which induced senescence-like phenotypes and affected cellular viability. We discovered that miR-34a potently targeted c-Myc and FoxM1, both of which were involved in the activation of telomerase reverse transcriptase (hTERT) transcription, essential for the sustaining activity of telomerase to avoid senescence. Taken together, our results demonstrate that miR-34a functions as a potent tumor suppressor through the modulation of telomere pathway in cellularsenescence. PMID:25686834

Increasing evidence suggests that miRNAs can act as either tumor suppressors or oncogenes in carcinogenesis. In the present study, we identified the role of miR-34a in regulating telomerase activity, with subsequent effect on cellularsenescence and viability. We found the higher expression of miR-34a was significantly correlated with the advanced clinicopathologic parameters in hepatocellular carcinoma. Furthermore, tumor tissues of 75 HCC patients demonstrated an inverse correlation between the miR-34a level and telomere indices (telomere length and telomerase activity). Transient introduction of miR-34a into HCC cell lines inhibited the telomerase activity and telomere length, which induced senescence-like phenotypes and affected cellular viability. We discovered that miR-34a potently targeted c-Myc and FoxM1, both of which were involved in the activation of telomerase reverse transcriptase (hTERT) transcription, essential for the sustaining activity of telomerase to avoid senescence. Taken together, our results demonstrate that miR-34a functions as a potent tumor suppressor through the modulation of telomere pathway in cellularsenescence. PMID:25686834

Long noncoding RNAs (lncRNAs) may play an important role in Alzheimer's disease (AD) pathogenesis. However, despite considerable research in this area, the comprehensive and systematic understanding of lncRNAs in AD is still limited. The emergence of RNA sequencing provides a predictor and has incomparable advantage compared with other methods, including microarray. In this study, we identified lncRNAs in a 7-month-old mouse brain through deep RNA sequencing using the senescence-accelerated mouse prone 8 (SAMP8) and senescence-accelerated mouse resistant 1 (SAMR1) models. A total of 599,985,802 clean reads and 23,334 lncRNA transcripts were obtained. Then, we identified 97 significantly upregulated and 114 significantly downregulated lncRNA transcripts from all cases in SAMP8 mice relative to SAMR1 mice. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes analyses revealed that these significantly dysregulated lncRNAs were involved in regulating the development of AD from various angles, such as nerve growth factor term (GO: 1990089), mitogen-activated protein kinase signaling pathway, and AD pathway. Furthermore, the most probable AD-associated lncRNAs were predicted and listed in detail. Our study provided the systematic dissection of lncRNA profiling in SAMP8 mouse brain and accelerated the development of lncRNA biomarkers in AD. These attracting biomarkers could provide significant insights into AD therapy in the future. PMID:27483026

The senescence-accelerated mouse prone 8 (SAMP8 mice) is known as a neurodegenerative model and may show age-related deficits of cognition. Curcumin, a major active component of spic turmeric, could increase the capacity of learning and memory in the aged rat. However, it is not known whether curcumin could improve cognitive deficits in SAMP8 mice. The present study was undertaken to evaluate the effect of curcumin on the learning and memory of SAMP8 mice and its possible mechanisms. Subjects were randomly divided into four groups: SAMR1 mice, SAMP8 mice and two SAMP8 mice groups treated, intragastrically, with curcumin at the dose of 20 and 50mg/kg per day, respectively. After 25days, spatial memory, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, p-calcium/calmodulin-dependent kinase II (p-CaMKII) and p-N-methyl-d-aspartate receptor subunit 1 (p-NMDAR1) expression in the hippocampus of mice were examined by using the Morris water maze, biochemical analysis, immunohistochemistry and Western blot. Compared with SAMR1 mice, SAMP8 mice had longer escape latency, higher MDA content, lower SOD activity in the hippocampus, and lower intensity of p-CaMKII in the stratum lucidum of hippocampal CA3 and p-NMDAR1 expression in the hippocampal membrane fraction. Both 20 and 50mg/kg curcumin administration significantly shortened the escape latencies and decreased the hippocampal MDA content in the SAMP8 mice. 50mg/kg curcumin administration significantly ameliorated the hippocampal SOD activity, and increased the intensity of p-CaMKII in the stratum lucidum of hippocampal CA3 and p-NMDAR1 expression in the hippocampal membrane fraction of the SAMP8 mice. The present study demonstrated that curcumin treatment could attenuate cognitive deficits of SAMP8 mice in a dose-dependent manner by decreasing the oxidative stress and improving the expression of p-CaMKII and p-NMDAR1 in the hippocampus. Thus treatment with curcumin may have a potential therapeutic agent

Activation of I-κB kinases (IKKs) and NF-κB by the human T lymphotropic virus type 1 (HTLV-1) trans-activator/oncoprotein, Tax, is thought to promote cell proliferation and transformation. Paradoxically, expression of Tax in most cells leads to drastic up-regulation of cyclin-dependent kinase inhibitors, p21(CIP1/WAF1) and p27(KIP1), which cause p53-/pRb-independent cellularsenescence. Here we demonstrate that p21(CIP1/WAF1)-/p27(KIP1)-mediated senescence constitutes a checkpoint against IKK/NF-κB hyper-activation. Senescence induced by Tax in HeLa cells is attenuated by mutations in Tax that reduce IKK/NF-κB activation and prevented by blocking NF-κB using a degradation-resistant mutant of I-κBα despite constitutive IKK activation. Small hairpin RNA-mediated knockdown indicates that RelA induces this senescence program by acting upstream of the anaphase promoting complex and RelB to stabilize p27(KIP1) protein and p21(CIP1/WAF1) mRNA respectively. Finally, we show that down-regulation of NF-κB by the HTLV-1 anti-sense protein, HBZ, delay or prevent the onset of Tax-induced senescence. We propose that the balance between Tax and HBZ expression determines the outcome of HTLV-1 infection. Robust HTLV-1 replication and elevated Tax expression drive IKK/NF-κB hyper-activation and trigger senescence. HBZ, however, modulates Tax-mediated viral replication and NF-κB activation, thus allowing HTLV-1-infected cells to proliferate, persist, and evolve. Finally, inactivation of the senescence checkpoint can facilitate persistent NF-κB activation and leukemogenesis. PMID:21552325

In the present investigation we aim to provide experimental information on and thereby understanding of the generation and propagation of spark-ignited, outwardly propagating cellular flames, with three major focuses. The first is to unambiguously demonstrate the influence of the four most important parameters in inducing hydrodynamic and diffusional-thermal cellularities, namely thermal expansion, flame thickness, non-unity Lewis number, and global activation energy. The second is to investigate the critical state for the onset of cellularity for the stretch-affected, expanding flame. The third is to identify and consequently quantify the phenomena of self-acceleration and possibly auto-turbulization of cellular flames. Due to space limitation the effects of activation energy and the critical state for the onset of cellularity will not be discussed herein. Experiments were conducted using C3H8-air and H2-O2-N2 mixtures for their opposite influences of non-equidiffusivity. The additional system parameters varied were the chamber pressure (p) and the mixture composition including the equivalence ratio (phi). From a sequence of the flame images we can assess the propensity of cell formation, and determine the instantaneous flame radius (R), the flame propagation rate, the global stretch rate experienced by the flame, the critical flame radius at which cells start to grow, and the average cell size.

Cellularsenescence suppresses cancer by halting the growth of premalignant cells, yet the accumulation of senescent cells is thought to drive age-related pathology through a senescence-associated secretory phenotype (SASP), the function of which is unclear. To understand the physiological role(s) of the complex senescent phenotype, we generated a mouse model in which senescent cells can be visualized and eliminated in living animals. We show that senescent fibroblasts and endothelial cells appear very early in response to a cutaneous wound, where they accelerate wound closure by inducing myofibroblast differentiation through the secretion of platelet-derived growth factor AA (PDGF-AA). In two mouse models, topical treatment of senescence-free wounds with recombinant PDGF-AA rescued the delayed wound closure and lack of myofibroblast differentiation. These findings define a beneficial role for the SASP in tissue repair and help to explain why the SASP evolved. PMID:25499914

Renal allograft survival is related directly to cell senescence. In the transplantation scenario many cellular events – participating as immunological and non-immunological factors – could contribute to accelerate this biological process, responsible for the ultimate fate of the graft. Mechanisms concerned in tolerance versus rejection are paramount in this outcome. For this reason, immunosuppressive treatment constitutes an extremely important decision to prevent organ dysfunction and, finally, graft loss. This study was conducted to document the proportion of CD4+/interleukin (IL)-17A+-, CD16+/indoleamine 2, 3-dioxygenase (IDO+)-, forkhead box protein P3 (FoxP3+)-expressing cells, senescent cells (p16INK4α) and the percentage of interstitial fibrosis (IF) in graft biopsies of kidney transplant recipients participating in the BENEFIT (Bristol-Myers Squibb IM103008) study. CD4+/IL-17A+, CD16+/IDO+, FoxP3+ and p16INK4α+ cells were evaluated by immunohistochemistry, and the percentage of IF by morphometry on graft biopsies obtained at time 0 (pre-implantation) and at 12 months post-transplant. Senescent cells and CD4+/IL-17A+ cells were increased among graft biopsies in subjects receiving cyclosporin A (CsA) compared to those under belatacept treatment. Meanwhile, CD16+/IDO+ and FoxP3+-expressing cells were lower in biopsies from CsA treatment compared to patients treated with Belatacept. Histological morphometric analyses disclosed more IF in 12-month CsA-treated patients in comparison to pre-implantation biopsy findings. Summing up, renal biopsies from patients receiving belatacept showed greater amounts of FoxP3+ cells and lower amounts of CD4+/IL-17A+ and senescent cells compared to patients under CsA treatment. Along with these findings, an increase in IF in annual CsA-treated-patients biopsies compared to pre-implantation and belatacept-treated patients were observed. PMID:22236010

Although the involvement of protein arginine methyltransferase 1 (PRMT1) in tumorigenesis has been reported, its roles in breast cancer progression and metastasis has not been elucidated. Here we identified PRMT1 as a key regulator of the epithelial-mesenchymal transition (EMT) in breast cancer. We showed that the EMT program induced by PRMT1 endowed the human mammary epithelial cells with cancer stem cell properties. Moreover, PRMT1 promoted the migratory and invasive behaviors in breast cancer cells. We also demonstrated that abrogation of PRMT1 expression in breast cancer cells abated metastasis in vivo in mouse model. In addition, knockdown of PRMT1 arrested cell growth in G1 tetraploidy and induced cellularsenescence. Mechanistically, PRMT1 impacted EMT process and cellularsenescence by mediating the asymmetric dimethylation of arginine 3 of histone H4 (H4R3me2as) at the ZEB1 promoter to activate its transcription, indicating the essential roles of this epigenetic control both in EMT and in senescence. Thus, we unraveled a dual function of PRMT1 in modulation of both EMT and senescence via regulating ZEB1. This finding points to the potent value of PRMT1 as a dual therapeutic target for preventing metastasis and for inhibiting cancer cell growth in malignant breast cancer patients. PMID:26813495

Sarcopenia is characterized by age-associated skeletal muscle atrophy and reduced muscle strength; currently, no pharmaceutical treatment is available. Go-sha-jinki-Gan (GJG) is a traditional Japanese herbal medicine that is used to alleviate various age-related symptoms, especially motor disorders. Here, we investigated the effect of GJG on aging-associated skeletal muscle atrophy by using senescence-accelerated mice (SAMP8). Immunohistochemical and western blotting analyses clearly showed that GJG significantly reduced the loss of skeletal muscle mass and ameliorated the increase in slow skeletal muscle fibers in SAMP8 mice compared to control mice. The expression levels of Akt and GSK-3β, the phosphorylation of FoxO4, and the phosphorylations of AMPK and mitochondrial-related transcription factors such as PGC-1α were suppressed, while the expression of MuRF1 increased in SAMP8 mice, but approximated that in senescence-accelerated aging-resistant (SAMR1) mice after GJG treatment. We demonstrate for the first time that GJG has a therapeutic effect against sarcopenia. PMID:25636865

Objective Relationship between microalbuminuria and worse outcome of coronary artery disease patients is discussed, but its underlying pathophysiological mechanism remains unclear. We investigated the role of microalbuminuria to the function of endothelial progenitor cells (EPCs), that might affect to outcome of acute myocardial infarction (AMI) patients. Methods Forty-five AMI patients were divided into two groups according to their urinary albumin excretion: normal (n = 24) and microalbuminuria (>30 mg/day, n = 21). At day-2 and day-7 after AMI onset, circulating-EPCs (CD34+Flk1+) were quantified by flow cytometry. The number of lectin-acLDL-positive cultured-EPCs immobilized on fibronectin was determined. To assess the cellularsenescence of cultured-EPCs, the expression level of sirtuin-1 mRNA and the number of SA-β-gal positive cell were evaluated. Angiographic late in-stent loss after percutaneous coronary intervention (PCI) was evaluated at a six-month follow-up. Results No significant differences in coronary risk and the extent of myocardial damage were observed between the two groups. Late in-stent loss at the six-month follow-up was significantly higher in the microalbuminuria group (normal : microalbuminuria = 0.76±0.34 : 1.18±0.57 mm, p=0.021). The number of circulating-EPCs was significantly increased in microalbuminuria group at day-7, however, improved adhesion of EPCs was observed in normal group but not in microalbuminuria group from baseline to day-7 (+3.1±8.3 : -1.3±4.4 %: p<0.05). On the other hand, in microalbuminuria group at day-7, the level of sirtuin-1 mRNA expression of cultured-EPCs was significantly decreased (7.1±8.9 : 2.5±3.7 fold, p<0.05), which was based on the negative correlation between the level of sirtuin-1 mRNA expression and the extent of microalbuminuria. The ratio of SA-β-gal-positive cells in microalbuminuria group was increased compared to that of normal group. Conclusions Microalbuminuria in AMI patients is

All-trans retinoic acid (ATRA) induces cellularsenescence via up-regulation of p16 and p21; however, the action mechanism of ATRA is unknown. Here, we show that ATRA induces promoter hypomethylation of p16 and p21 via down-regulation of DNA methyltransferases 1, 3a, and 3b to facilitate binding of Ets1/2 to the p16 promoter and p53 to the p21 promoter, resulting in up-regulation of their expression and subsequent induction of cellularsenescence in HepG2 cells. These effects were mediated by retinoic acid receptor β₂ whose promoter was also hypomethylated in the presence of ATRA. Therefore, ATRA can be considered as an epi-drug in cancer therapy. PMID:21843507

Expression of oncogenic K-RAS in primary cells elicits oncogene-induced cellularsenescence (OIS), a form of growth arrest that potently opposes tumourigenesis. This effect has been largely attributed to transcriptional mechanisms that depend on the p53 tumour suppressor protein. The PML tumour suppressor was initially identified as a component of the PML-RARα oncoprotein of acute promyelocytic leukaemia (APL). PML, a critical OIS mediator, is upregulated by oncogenic K-RAS in vivo and in vitro. We demonstrate here that oncogenic K-RAS induces PML protein upregulation by activating the RAS/MEK1/mTOR/eIF4E pathway even in the absence of p53. Under these circumstances, PML mRNA is selectively associated to polysomes. Importantly, we find that the PML 5′ untranslated mRNA region plays a key role in mediating PML protein upregulation and that its presence is essential for an efficient OIS response. These findings demonstrate that upregulation of PML translation plays a central role in oncogenic K-RAS-induced OIS. Thus, selective translation initiation plays a critical role in tumour suppression with important therapeutic implications for the treatment of solid tumours and APL. PMID:22359342

Annually, ovarian cancer (OC) affects 240,000 women worldwide and is the most lethal gynecological malignancy. High-grade serous OC (HGSOC) is the most common and aggressive OC subtype, characterized by widespread genome changes and chromosomal instability and is consequently poorly responsive to chemotherapy treatment. The objective of this study was to investigate the role of the microRNA miR-433 in the cellular response of OC cells to paclitaxel treatment. We show that stable miR-433 expression in A2780 OC cells results in the induction of cellularsenescence demonstrated by morphological changes, downregulation of phosphorylated retinoblastoma (p-Rb), and an increase in β-galactosidase activity. Furthermore, in silico analysis identified four possible miR-433 target genes associated with cellularsenescence: cyclin-dependent kinase 6 (CDK6), MAPK14, E2F3, and CDKN2A. Mechanistically, we demonstrate that downregulation of p-Rb is attributable to a miR-433-dependent downregulation of CDK6, establishing it as a novel miR-433 associated gene. Interestingly, we show that high miR-433 expressing cells release miR-433 into the growth media via exosomes which in turn can induce a senescence bystander effect. Furthermore, in relation to a chemotherapeutic response, quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that only PEO1 and PEO4 OC cells with the highest miR-433 expression survive paclitaxel treatment. Our data highlight how the aberrant expression of miR-433 can adversely affect intracellular signaling to mediate chemoresistance in OC cells by driving cellularsenescence. PMID:25684390

Lrf has been previously described as a powerful proto-oncogene. Here we surprisingly demonstrate that Lrf plays a critical oncosuppressive role in the prostate. Prostate specific inactivation of Lrf leads to a dramatic acceleration of Pten-loss-driven prostate tumorigenesis through a bypass of Pten-loss-induced senescence (PICS). We show that LRF physically interacts with and functionally antagonizes SOX9 transcriptional activity on key target genes such as MIA, which is involved in tumor cell invasion, and H19, a long non-coding RNA precursor for an Rb-targeting miRNA. Inactivation of Lrf in vivo leads to Rb down-regulation, PICS bypass and invasive prostate cancer. Importantly, we found that LRF is genetically lost, as well as down-regulated at both the mRNA and protein levels in a subset of human advanced prostate cancers. Thus, we identify LRF as a context-dependent cancer gene that can act as an oncogene in some contexts but also displays oncosuppressive-like activity in Pten−/− tumors. PMID:23727861

MYC-induced T-ALL exhibit oncogene addiction. Addiction to MYC is a consequence of both cell-autonomous mechanisms, such as proliferative arrest, cellularsenescence, and apoptosis, as well as non-cell autonomous mechanisms, such as shutdown of angiogenesis, and recruitment of immune effectors. Here, we show, using transgenic mouse models of MYC-induced T-ALL, that the loss of either p19ARF or p53 abrogates the ability of MYC inactivation to induce sustained tumor regression. Loss of p53 or p19ARF, influenced the ability of MYC inactivation to elicit the shutdown of angiogenesis; however the loss of p19ARF, but not p53, impeded cellularsenescence, as measured by SA-beta-galactosidase staining, increased expression of p16INK4A, and specific histone modifications. Moreover, comparative gene expression analysis suggested that a multitude of genes involved in the innate immune response were expressed in p19ARF wild-type, but not null, tumors upon MYC inactivation. Indeed, the loss of p19ARF, but not p53, impeded the in situ recruitment of macrophages to the tumor microenvironment. Finally, p19ARF null-associated gene signature prognosticated relapse-free survival in human patients with ALL. Therefore, p19ARF appears to be important to regulating cellularsenescence and innate immune response that may contribute to the therapeutic response of ALL. PMID:25784651

Fusarium oxysporum f.sp. cubense (FOC) is a causal agent of vascular wilt and leaf chlorosis of banana plants. Chloroses resulting from FOC occur first in the lowest leaves of banana seedlings and gradually progress upward. To investigate the responses of different leaf positions to FOC infection, hydroponic experiments with FOC inoculation were conducted in a greenhouse. Fusarium-infected seedlings exhibited a decrease in net photosynthesis rate, stomatal conductance, and transpiration rate of all leaves. The wilting process in Fusarium-infected seedlings varied with leaf position. Measurements of the maximum photochemical efficiency of photosystem II (F(V)/F(max) and visualization with transmission electron microscopy showed a positive correlation between chloroplast impairment and severity of disease symptoms. Furthermore, results of malondialdehyde content and relative membrane conductivity measurements demonstrated that the membrane system was damaged in infected leaves. Additionally, the activities of phenylalanine ammonia-lyase, peroxidase and polyphenol oxidase were increased and total soluble phenolic compounds were significantly accumulated in the leaves of infected plants. The structural and biochemical changes of infected plants was consistent with plant senescence. As the FOC was not detected in infected leaves, we proposed that the chloroplast and membrane could be damaged by fusaric acid produced by Fusarium. During the infection, fusaric acid was first accumulated in the lower leaves and water-soluble substances in the lower leaves could dramatically enhance fusaric acid production. Taken together, the senescence of infected banana plants was induced by Fusarium infection with fusaric acid production and the composition of different leaf positions largely contribute to the particular senescence process. PMID:24282097

Two members of the senescence-accelerated mouse group, SAMP8 and SAMP10, are characterized by learning and memory deficits, while the SAMR1 strain is not. In this study, we used two behavioral tests, social approach and object recognition and compared the results observed for the SAMP strains with those seen in the control strain, SAMR1. In social approach experiments, the 2 SAMP strains showed decreased sociability compared to SAMR1 as shown by their reluctance to spend time near a stranger mouse and increased immobility. In object recognition experiments, SAMP strains spent more time in the thigmotaxis zone and less time in the more exposed central zone than SAMR1 mice. From a behavioral standpoint, SAMP mice were less interactive and showed increased anxiety-like behavior compared to SAMR1. PMID:23672852

Senescenceaccelerated mice P8 (SAMP8) is a phenotypic model of age, characterized by deficits in memory and altered behaviour. Here, we determined the effect of age in SAMP8, and compared with the resistant strain, SAMR1, in behaviour and learning parameters linking these disturbances with oxidative stress environment. We found impairment in emotional behaviour with regard to fear and anxiety in young SAMP8 vs. age-mated SAMR1. Differences were attenuated with age. In contrast, learning capabilities are worse in SAMP8, both in young and aged animals, with regard to SAMR1. These waves in behaviour and cognition were correlated with an excess of oxidative stress (OS) in SAMP8 at younger ages that diminished with age. In this manner, we found changes in the hippocampal expression of ALDH2, IL-6, HMOX1, COX2, CXCL10, iNOS, and MCP-1 with an altered amyloidogenic pathway by increasing the Amyloid beta precursor protein (APP) and BACE1, and reduced ADAM10 expression; in addition, astrogliosis and neuronal markers decreased. Moreover, Superoxide dismutase 1 (SOD1) and Nuclear factor-kappa beta (NF-kβ) expression and protein levels were higher in younger SAMP8 than in SAMR1. In conclusion, the acceleratedsenescence process present in SAMP8 can be linked with an initial deregulation in redox homeostasis, named neuroinflammaging, by inducing molecular changes that lead to neuroinflammation and the neurodegenerative process. These changes are reflected in the emotional and cognitive behaviour of SAMP8 that differs from that of SAMR1 and that highlighted the importance of earlier oxidative processes in the onset of neurodegeneration. PMID:27094468

Current understanding points to unrepairable chromosomal damage as the critical determinant of acceleratedsenescence in cancer cells treated with radiation or chemotherapy. Nonetheless, the potent senescence inducer etoposide not only targets topoisomerase II to induce DNA damage but also produces abundant free radicals, increasing cellular reactive oxygen species (ROS). Toward examining roles for DNA damage and oxidative stress in therapy-induced senescence, we developed a quantitative flow cytometric senescence assay and screened 36 redox-active agents as enhancers of an otherwise ineffective dose of radiation. While senescence failed to correlate with total ROS, the radiation enhancers, etoposide and the other effective topoisomerase inhibitors each produced high levels of lipid peroxidation. The reactive aldehyde 4-hydroxy-2-nonenal, a lipid peroxidation end product, was sufficient to induce senescence in irradiated cells. In turn, sequestering aldehydes with hydralazine blocked effects of etoposide and other senescence inducers. These results suggest that lipid peroxidation potentiates DNA damage from radiation and chemotherapy to drive therapy-induced senescence. PMID:27453792

The influence of two known cardiovascular risk factors, aging and consumption of a high-fat diet, on vascular mesenteric artery reactivity was examined in a mouse model of acceleratedsenescence (SAM). Five-month-old SAM prone (SAMP8) and resistant (SAMR1) female mice were fed a Western-type high-fat diet (WD; 8 weeks). Mesenteric arteries were dissected, and vascular reactivity, protein and messenger RNA expression, superoxide anion (O 2 (·-) ) and hydrogen peroxide formation were evaluated by wire myography, immunofluorescence, RT-qPCR, ethidium fluorescence and ferric-xylenol orange, respectively. Contraction to KCl and relaxation to acetylcholine remained unchanged irrespective of senescence and diet. Although similar contractions to phenylephrine were observed in SAMR1 and SAMP8, acceleratedsenescence was associated with decreased eNOS and nNOS and increased O 2 (·-) synthesis. Senescence-related alterations were compensated, at least partly, by the contribution of NO derived from iNOS and the enhanced endogenous antioxidant capacity of superoxide dismutase 1 to maintain vasoconstriction. Administration of a WD induced qualitatively different alterations in phenylephrine contractions of mesenteric arteries from SAMR1 and SAMP8. SAMR1 showed increased contractions partly as a result of decreased NO availability generated by decreased eNOS and nNOS and enhanced O 2 (·-) formation. In contrast, WD feeding in SAMP8 resulted in reduced contractions due to, at least in part, the increased functional participation of iNOS-derived NO. In conclusion, senescence-dependent intrinsic alterations during early stages of vascular senescence may promote vascular adaptation and predispose to further changes in response to high-fat intake, which may lead to the progression of aging-related cardiovascular disease, whereas young subjects lack the capacity for this adaptation. PMID:22777652

Amyloid beta-peptide (Abeta) is the major constituent of senile plaques, a pathological hallmark of Alzheimer's disease (AD) brain. It is generally accepted that Abeta plays a central role in the pathophysiology of AD. Abeta is released from cells under entirely normal cellular conditions during the internalization and endosomal processing of amyloid precursor protein (APP). However, accumulation of Abeta can induce neurotoxicity. Our previous reports showed that decreasing the production of Abeta by giving an intracerebroventricular injection of a 42-mer phosphorothiolated antisense oligonucleotide (AO) directed at the Abeta region of the APP gene reduces lipid peroxidation and protein oxidation and improves cognitive deficits in aged senescence-accelerated mice prone 8 (SAMP8) mice. In order to investigate how Abeta level reduction improves learning and memory performance of SAMP8 mice through reduction of oxidative stress in brains, we used proteomics to identify the proteins that are less oxidized in 12-month-old SAMP8 mice brains treated with AO against the Abeta region of APP (12 mA) compared to that of the age-control SAMP8 mice. We found that the specific protein carbonyl levels of aldoase 3 (Aldo3), coronin 1a (Coro1a) and peroxiredoxin 2 (Prdx2) are significantly decreased in the brains of 12 mA SAMP8 mice compared to the age-controlled SAMP8 treated with random AO (12 mR). We also found that the expression level of alpha-ATP synthase (Atp5a1) was significantly decreased, whereas the expression of profilin 2 (Pro-2) was significantly increased in brains from 12 mA SAMP8 mice. Our results suggest that decreasing Abeta levels in aged brain in aged accelerated mice may contribute to the mechanism of restoring the learning and memory improvement in aged SAMP8 mice and may provide insight into the role of Abeta in the memory and cognitive deficits in AD. PMID:15932783

We studied potential changes in the subventricular zone (SVZ) stem cell niche of the senescence-accelerated mouse prone-8 (SAM-P8) aging model. Bromodeoxyuridine (BrdU) assays with longtime survival revealed a lower number of label-retaining stem cells in the SAM-P8 SVZ compared with the SAM-Resistant 1 (SAM-R1) control strain. We also found that in SAM-P8 niche signaling is attenuated and the stem cell pool is less responsive to the self-renewal niche factor pigmented epithelium-derived factor (PEDF). Protein analysis demonstrated stable amounts of the PEDF ligand in the SAM-P8 SVZ niche; however, SAM-P8 stem cells present a significant expression decrease of patatin-like phospholipase domain containing 2, a receptor for PEDF (PNPLA2-PEDF) receptor, but not of laminin receptor (LR), a receptor for PEDF (LR-PEDF) receptor. We observed changes in self-renewal related genes (hairy and enhancer of split 1 (Hes1), hairy and enhancer of split 1 (Hes5), Sox2] and report that although these genes are down-regulated in SAM-P8, differentiation genes (Pax6) are up-regulated and neurogenesis is increased. Finally, sheltering mammalian telomere complexes might be also involved given a down-regulation of telomeric repeat binding factor 1 (Terf1) expression was observed in SAM-P8 at young age periods. Differences between these 2 models, SAM-P8 and SAM-R1 controls, have been previously detected at more advanced ages. We now describe alterations in the PEDF signaling pathway and stem cell self-renewal at a very young age, which could be involved in the premature senescence observed in the SAM-P8 model. PMID:25636741

In this work, metabonomic methods utilizing (1)H NMR spectroscopy and multivariate statistical technique have been applied to investigate the metabolic profiles of SAM. The serum metabolome of senescence-prone 8 (SAMP8), a murine model of age-related learning and memory deficits and Alzheimer's disease (AD), was compared with that of control, senescence-resistant 1 (SAMR1), which shows normal aging process. Serum samples were collected for study from both male and female 12-month-old SAMP8 and age matched SAMR1 ( n = 5). (1)H NMR spectra of serum were analyzed by pattern recognition using principal components analysis. The results showed that the serum metabolic patterns of SAMP8 and SAMR1 were significantly different due to strains and genders. Subtle differences in the endogenous metabolite profiles in serum between SAMP8 and SAMR1 were observed. The most important metabolite responsible for the strain separation was lack of inosine, which meant the protective function of anti-inflammation, immunomodulation and neuroprotection might be attenuated in SAMP8. Other differential metabolites observed between strains included decreased glucose, PUFA, choline, phosphocholine, HDL, LDL, D-3-hydoxybutyrate, citrate and pyruvate and increased lactate, SFA, alanine, methionine, glutamine and VLDL in serum of SAMP8 compared with those of SAMR1, suggesting perturbed glucose and lipid metabolisms in SAMP8. Besides the differences observed between the strains, an impact of gender on metabolism was also found. The females exhibited larger metabolic deviations than males and these gender differences in SAMP8 were much larger than in SAMR1. Higher levels of VLDL, lactate and amino acids and lower levels of HDL, LDL and unsaturated lipids were detected in female than in male SAMP8. These facts indicated that the metabolism disequilibrium in female and male SAMP8 was different and this may partly explain that females were more prone to AD than males. The results of this work may

The senescence-accelerated mouse (SAM) is used as an animal model of senescenceacceleration and age-associated disorders. SAM is derived from unexpected crosses between the AKR/J and unknown mouse strains. There are nine senescence-prone (SAMP) strains and three senescence-resistant (SAMR) strains. Although SAMP strains exhibit strain-specific and age-related pathological changes, the genes responsible for the pathologic changes in SAMP strains have not been comprehensively identified. In the present study, we evaluated sweet taste perception using the two-bottle test. We compared genotypes of the taste related gene, Tas1r3, using SAM strains and the parental AKR/J strain. The two-bottle test revealed that SAMR1 (R1), SAMP6 (P6), SAMP8 (P8), and SAMP10 (P10) mice were saccharin-preferring strains, whereas AKR/J did not prefer saccharin. All genotypes of the R1, P6, P8, and P10 strains at the polymorphic sites in Tas1r3, which is known to influence saccharin preference, were identical to those of C57BL6/J, a well-known saccharin-preferring strain, and were completely different from those of the parental AKR/J strain. These genetic alterations in SAM strains appear to arise from an unknown strain that is thought to have been crossed with AKR/J initially. PMID:24726396

Oncogene-induced senescence is an anti-proliferative stress response program that acts as a fail-safe mechanism to limit oncogenic transformation and is regulated by the retinoblastoma protein (RB) and p53 tumor suppressor pathways. We identify the atypical E2F family member E2F7 as the only E2F transcription factor potently up-regulated during oncogene-induced senescence, a setting where it acts in response to p53 as a direct transcriptional target. Once induced, E2F7 binds and represses a series of E2F target genes and cooperates with RB to efficiently promote cell cycle arrest and limit oncogenic transformation. Disruption of RB triggers a further increase in E2F7, which induces a second cell cycle checkpoint that prevents unconstrained cell division despite aberrant DNA replication. Mechanistically, E2F7 compensates for the loss of RB in repressing mitotic E2F target genes. Together, our results identify a causal role for E2F7 in cellularsenescence and uncover a novel link between the RB and p53 pathways. PMID:22802529

The role of the magnocellular reticular formation (MGRF) of the brainstem on learning and memory was examined in memory-deficient mice with spontaneous spongy degeneration in the brainstem (senescence-accelerated mouse, SAMP8) and control mice (accelerated-senescence resistant mouse, SAMR 1). SAMP8 showed spontaneous age-related impairment of learning and memory, as determined by passive and active avoidance responses. The deficits of learning and memory function in passive avoidance performances began at two months of age and increased with ageing. In the brains of SAMP8 at one month of age and older, spongy degeneration was mainly observed in the brainstem, while no vacuoles were evident in SAMR1 control (normal ageing mouse) brains in the age range tested (up to 12 months). The vacuolization in SAMP8 was marked in the MGRF, especially in the dorsomedial MGRF. Quantitative analysis of the vacuolization showed that the total area and number of vacuoles in the MGRF increased with age, and they were affected by the degree of deficits in learning and memory. The latency 24 h after footshock in passive avoidance tests decreased with the increase in total area and number of vacuoles in MGRF. The number of shocks in active avoidance tests increased with the increase in total number and area of vacuoles. Thus, learning and memory ability in passive and active avoidance responses deteriorated with enlargement in the vacuolated area in MGRF, and it was assumed that MGRF (especially, the dorsomedial part) possesses functions related to learning and memory. To confirm this notion, behavior and memory tests (passive avoidance and active avoidance tests, open field tests and shock sensitivity measurements) were carried out in SAMR1 mice, whose bilateral dorsomedial MGRF was destroyed electrolytically (MGRF-lesioned mice). The MGRF-lesioned mice showed no difference from sham mice in sensory threshold or open field activity; however, there was severe deterioration in passive

Background Etiology of complex disorders, such as cataract and neurodegenerative diseases including age-related macular degeneration (AMD), remains poorly understood due to the paucity of animal models, fully replicating the human disease. Previously, two quantitative trait loci (QTLs) associated with early cataract, AMD-like retinopathy, and some behavioral aberrations in senescence-accelerated OXYS rats were uncovered on chromosome 1 in a cross between OXYS and WAG rats. To confirm the findings, we generated interval-specific congenic strains, WAG/OXYS-1.1 and WAG/OXYS-1.2, carrying OXYS-derived loci of chromosome 1 in the WAG strain. Both congenic strains displayed early cataract and retinopathy but differed clinically from OXYS rats. Here we applied a high-throughput RNA sequencing (RNA-Seq) strategy to facilitate nomination of the candidate genes and functional pathways that may be responsible for these differences and can contribute to the development of the senescence-accelerated phenotype of OXYS rats. Results First, the size and map position of QTL-derived congenic segments were determined by comparative analysis of coding single-nucleotide polymorphisms (SNPs), which were identified for OXYS, WAG, and congenic retinal RNAs after sequencing. The transferred locus was not what we expected in WAG/OXYS-1.1 rats. In rat retina, 15442 genes were expressed. Coherent sets of differentially expressed genes were identified when we compared RNA-Seq retinal profiles of 20-day-old WAG/OXYS-1.1, WAG/OXYS-1.2, and OXYS rats. The genes most different in the average expression level between the congenic strains included those generally associated with the Wnt, integrin, and TGF-β signaling pathways, widely involved in neurodegenerative processes. Several candidate genes (including Arhgap33, Cebpg, Gtf3c1, Snurf, Tnfaip3, Yme1l1, Cbs, Car9 and Fn1) were found to be either polymorphic in the congenic loci or differentially expressed between the strains. These genes may

Aging is associated with an increase in oxidative stress and inflammation. The aging lung is particularly affected since it is continuously exposed to environmental oxidants while antioxidant machinery weakens with age. Melatonin, a free radical scavenger, counteracts inflammation and apoptosis in healthy cells from several tissues. Its effects on the aging lung are, however, not yet fully understood. This study aimed to investigate the effect of chronic administration of melatonin on the expression of inflammation markers (TNF-α, IL-1β, NFκB2, HO-1) and apoptosis parameters (BAD, BAX, AIF) in the lung tissue of male senescence-accelerated prone mice (SAMP8). In addition, RNA oxidative damage, as the formation of 8-hydroxyguanosine (8-OHG), was also evaluated. Young and old animals, aged 2 and 10 months respectively, were divided into 4 groups: untreated young, untreated old, old mice treated with 1mg/kg/day melatonin, and old animals treated with 10mg/kg/day melatonin. Untreated young and old male senescenceaccelerated resistant mice (SAMR1) were used as controls. After 30 days of treatment, animals were sacrificed. Lungs were collected and immediately frozen in liquid nitrogen. mRNA and protein expressions were measured by RT-PCR and Western blotting, respectively. Levels of 8-OHG were quantified by ELISA. Mean values were analyzed using ANOVA. Old nontreated SAMP8 animals showed increased (p<0.05) mRNA and protein levels of TNF-α, IL-1β, NFκB2, and HO-1 compared to young mice and SAMR1 mice. Melatonin treatment with either dose reversed the aging-derived inflammation (p<0.05). BAD, BAX and AIF expressions also rose with aging, the effect being counteracted with melatonin (p<0.05). Aging also caused a significant elevation (p<0.05) in SAMP8 8-OHG values. This increase was not observed in animals treated with melatonin (p<0.05). In conclusion, melatonin treatment was able to modulate the inflammatory and apoptosis status of the aging lungs, exerting a

3,3′,4,4′,5,5′-Hexahydroxy-trans-stilbene (M8) is a synthetic resveratrol derivative, advertised as a candidate drug highly effective against numerous malignancies. Because multiple tumors prone to M8 frequently metastasize into the peritoneal cavity, this study was aimed at establishing the effect of M8 on the growth and senescence of human peritoneal mesothelial cells (HPMCs), the largest cell population within the peritoneum, actively involved in the intraperitoneal spread of cancer. The study showed that M8, used at the highest non-toxic dose of 10 μM, impairs proliferation and acceleratessenescence in cultured HPMCs via an oxidative stress-dependent mechanism. At the same time, soluble factors released to the environment by HPMCs that senesced prematurely in response to M8 promoted growth of colorectal and pancreatic carcinomas in vitro. These findings indicate that M8 may indirectly—through the modification of normal (mesothelial) cells phenotype—facilitate an expansion of cancer cells, which challenges the postulated value of this stilbene in chemotherapy. PMID:24240809

d-Glucose metabolism in cerebral cells prepared from aged senescence-accelerated mouse (SAM), was investigated in consideration of a sex difference. The production of 14CO2 from 6-[14C]D-glucose was reduced in female senescence-accelerated-prone mouse (SAMP) 8, a prone substrain, in comparison with that in female senescence-accelerated-resistant mouse (SAMR) 2, a control substrain, whereas there was no difference in males. The 2-deoxy-D-glucose uptake into cerebral cells from female SAMP8 was also lower than that of control mice. But, the 3-O-methyl-D-glucose uptake in SAMP8 was higher than that of SAMR2, suggesting that the low hexokinase activity was involved in the decreased glucose metabolism in cerebrum of SAMP8 females irrespective of glucose transporter. This possibility was supported by the finding that the contents of glucose 6-phosphate produced from glucose added to cerebral cells from SAMP8 was lower than that in ICR mice. PMID:8873128

The senescenceaccelerated mouse (SAM) is known as a murine model of aging. SAM consists of senescenceaccelerated-prone mouse (SAMP) and senescenceaccelerated-resistant mouse (SAMR). Previous studies reported that SAMP10 exhibits age-related learning impairments and behavioral depression in a tail suspension test after 7 months. We investigated the changes in emotional behavior in a forced swimming test and in receptors for dopamine and 5-hydroxytryptamine (5-HT) in SAMP10. SAMP10 at 8 months showed an increase of immobility in the test compared with SAMR1. Treatment with desipramine (25 mg/kg, i.p., 3 days) in SAMP10 caused a decrease in immobility. In the cortex from SAMP10, [3H]quinpirole binding to D2/D3 dopamine receptors increased significantly compared with control SAMR1. In the hippocampus from SAMP10, [3H]8-hydroxy DPAT binding to 5-HT1A receptor increased. In midbrains from SAMP10, bindings of [3H]quinpirole and [3H]8-hydroxy DPAT increased. [3H]SCH23390 binding to D1/D5 receptors and [3H]ketanserin binding to 5-HT2 receptor in brain regions examined in SAMP10 were similar to those in SAMR1. The present findings represent the first neurochemical evidence of an increase of D2/D3 and 5-HT1A receptors in SAMP10. SAMP10 may be a useful model of aging associated depressive behavior. PMID:11001177

Hybrid chlorosis, a type of hybrid incompatibility, has frequently been reported in inter- and intraspecific crosses of allopolyploid wheat. In a previous study, we reported some types of growth abnormalities such as hybrid necrosis and observed hybrid chlorosis with mild or severe abnormalities in wheat triploids obtained in crosses between tetraploid wheat cultivar Langdon and four Ae. tauschii accessions and in their derived synthetic hexaploids. However, the molecular mechanisms underlying hybrid chlorosis are not well understood. Here, we compared cytology and gene expression in leaves to characterize the abnormal growth in wheat synthetics showing mild and severe chlorosis. In addition, we compared disease resistance to wheat blast fungus. In total 55 and 105 genes related to carbohydrate metabolism and 53 and 89 genes for defense responses were markedly up-regulated in the mild and severe chlorosis lines, respectively. Abnormal chloroplasts formed in the mesophyll cells before the leaves yellowed in the hybrid chlorosis lines. The plants with mild chlorosis showed increased resistance to wheat blast and powdery mildew fungi, although significant differences only in two, third internode length and maturation time, out of the examined agricultural traits were found between the wild type and plants showing mild chlorosis. These observations suggest that senescence might be accelerated in hybrid chlorosis lines of wheat synthetics. Moreover, in wheat synthetics showing mild chlorosis, the negative effects on biomass can be minimized, and they may show substantial fitness under pathogen-polluted conditions. PMID:25806790

Increases in the number of patients with dementia involving Alzheimer's disease (AD) are seen as a grave public health problem. In neurodegenerative disorders involving AD, biological stresses, such as oxidative and inflammatory stress, induce neural cell damage. Asparagus (Asparagus officinalis) is a popular vegetable, and an extract prepared from this reportedly possesses various beneficial biological activities. In the present study, we investigated the effects of enzyme-treated asparagus extract (ETAS) on neuronal cells and early cognitive impairment of senescence-accelerated mouse prone 8 (SAMP8) mice. The expression of mRNAs for factors that exert cytoprotective and anti-apoptotic functions, such as heat-shock protein 70 and heme oxygenase-1, was upregulated in NG108-15 neuronal cells by treatment with ETAS. Moreover, when release of lactate dehydrogenase from damaged NG108-15 cells was increased for cells cultured in medium containing either the nitric oxide donor sodium nitroprusside or the hypoxia mimic reagent cobalt chloride, ETAS significantly attenuated this cell damage. Also, when contextual fear memory, which is considered to be a hippocampus-dependent memory, was significantly impaired in SAMP8 mice, ETAS attenuated the cognitive impairment. These results suggest that ETAS produces cytoprotective effects in neuronal cells and attenuates the effects on the cognitive impairment of SAMP8 mice. PMID:24660475

Hybrid chlorosis, a type of hybrid incompatibility, has frequently been reported in inter- and intraspecific crosses of allopolyploid wheat. In a previous study, we reported some types of growth abnormalities such as hybrid necrosis and observed hybrid chlorosis with mild or severe abnormalities in wheat triploids obtained in crosses between tetraploid wheat cultivar Langdon and four Ae. tauschii accessions and in their derived synthetic hexaploids. However, the molecular mechanisms underlying hybrid chlorosis are not well understood. Here, we compared cytology and gene expression in leaves to characterize the abnormal growth in wheat synthetics showing mild and severe chlorosis. In addition, we compared disease resistance to wheat blast fungus. In total 55 and 105 genes related to carbohydrate metabolism and 53 and 89 genes for defense responses were markedly up-regulated in the mild and severe chlorosis lines, respectively. Abnormal chloroplasts formed in the mesophyll cells before the leaves yellowed in the hybrid chlorosis lines. The plants with mild chlorosis showed increased resistance to wheat blast and powdery mildew fungi, although significant differences only in two, third internode length and maturation time, out of the examined agricultural traits were found between the wild type and plants showing mild chlorosis. These observations suggest that senescence might be accelerated in hybrid chlorosis lines of wheat synthetics. Moreover, in wheat synthetics showing mild chlorosis, the negative effects on biomass can be minimized, and they may show substantial fitness under pathogen-polluted conditions. PMID:25806790

Alzheimer's disease (AD) is characterized by the progressive accumulation of extracellular β-amyloid (Aβ) aggregates. Recently, the senescence-accelerated mouse-prone 8 (SAMP8) model was highlighted as a useful model of age-related AD. Therefore, we used the SAMP8 mouse to investigate the preventive effects of sesame lignans on the onset of AD-like pathology. In preliminary in vitro studies, sesaminol showed the greatest inhibitory effect on Aβ oligomerization and fibril formation relative to sesamin, sesamolin, and sesaminol triglucoside. Hence, sesaminol was selected for further evaluation in vivo. In SAMP8 mice, feed-through sesaminol (0.05%, w/w, in standard chow) administered over a 16 week period reduced brain Aβ accumulation and decreased serum 8-hydroxydeoxyguanosine, an indicator of oxidative stress. Furthermore, sesaminol administration increased the gene and protein expression of ADAM10, which is a protease centrally involved in the non-amyloidogenic processing of amyloid precursor protein. Taken together, these data suggest that long-term consumption of sesaminol may inhibit the accumulation of pathogenic Aβ in the brain. PMID:27233432

-related genes allow a framework to be constructed of decisive events in the evolution of the senescence syndrome of modern land-plants. Combining phylogenetic, comparative sequence, gene expression and morphogenetic information leads to the conclusion that biochemical, cellular, integrative and adaptive systems were progressively added to the ancient primary core process of senescence as the evolving plant encountered new environmental and developmental contexts. PMID:19602260

The incidence of chromosome aberrations in bone marrow cells of 12-month-old SAMP-1 female mice characterized by accelerated aging was 1.8 times higher than in wild-type SAMR-1 females and 2.2 times higher than in SHR females of the same age. Treatment with Epithalon (Ala-Glu-Asp-Gly) starting from the age of 2 months decreased the incidence of chromosome aberrations in SAMP-1, SAMR-1, and SHR mice by 20%, 30.1%, and 17.9%, respectively, compared to age-matched controls (p<0.05). Treatment with melatonin (given with drinking water in a dose of 20 mg/liter in night hours) had no effect on the incidence of chromosome aberrations in SHR mice. These data indicate antimutagenic effect of Epithalon, which probably underlies the geroprotective effect of this peptide. PMID:12360351

The cerebella of SAMP(8) (accelerated aging mouse) and SAMR(1) controls were analyzed by Western Blotting of tyrosine hydroxylase and choline acetyltransferase, as well as by TUNEL and histological silver staining. Both tyrosine hydroxylase and choline acetyltransferase levels were higher in SAMR(1) than in SAMP(8). There was also an age-related decrease in enzyme levels in SAMP(8), with the reduction of tyrosine hydroxylase being more apparent. Concomitantly, there was an age-related increase of apoptosis in the medial neocerebellum and the vermis as revealed by TUNEL, with changes being significant in the SAMP(8) strain. Histologically, some Purkinje cells appeared to disappear during aging. Taken together, the data suggests that the aging SAMP(8) strain displays differential Purkinje cell death in the medial cerebellum and that some of the dying cells are likely to be catecholaminergic. PMID:17415677

H-Ras oncogene requires deregulation of additional oncogenes or inactivation of tumor suppressor proteins to increase cell proliferation rate and transform cells. In fact, the expression of the constitutively activated H-RasV12 induces cell growth arrest and premature senescence, which act like barriers in pre-neoplastic lesions. In our experimental model, human fibroblasts transfected with H-RasV12 show a dramatic modification of morphology. H-RasV12 expressing cells also show premature senescence followed by cell death, induced by autophagy and apoptosis. In this context, we provide evidence that in H-RasV12 expressing cells, the premature senescence is associated with cellular redox imbalance as well as with altered post-translation protein modification. In particular, redox imbalance is due to a strong reduction of total antioxidant capacity, and significant decrease of glutathione level. As the reversible addition of glutathione to cysteinyl residues of proteins is an important post-translational regulative modification, we investigated S-glutathionylation in cells expressing active H-Ras. In this contest we observed different S-glutathionylation patterns in control and H-RasV12 expressing cells. Particularly, the GAPDH enzyme showed S-glutathionylation increase and significant enzyme activity depletion in H-Ras V12 cells. In conclusion, we proposed that antioxidant defense reduction, glutathione depletion and subsequent modification of S-glutathionylation of target proteins contribute to arrest cell growth, leading to death of fibroblasts expressing constitutively active H-Ras oncogene, thus acting as oncogenic barriers that obstacle the progression of cell transformation. PMID:23284910

Progressively sophisticated understanding of cellular and molecular processes that contribute to age-related physical deterioration is being gained from ongoing research into cancer, chronic inflammatory syndromes and other serious disorders that increase with age. Particularly valuable insight has resulted from characterization of how senescent cells affect the tissues in which they form in ways that decrease an organism's overall viability. Increasingly, the underlying pathophysiology of ageing is recognized as a consequence of oxidative damage. This leads to hyperactivity of cell growth pathways, prominently including mTOR (mammalian target of rapamycin), that contribute to a build-up in cells of toxic aggregates such as progerin (a mutant nuclear cytoskeletal protein), lipofuscin and other cellular debris, triggering formation of senescentcellular phenotypes, which interact destructively with surrounding tissue. Indeed, senescent cell ablation dramatically inhibits physical deterioration in progeroid (age-accelerated) mice. This review explores ways in which oxidative stress creates ageing-associated cellular damage and triggers induction of the cell death/survival programs' apoptosis, necrosis, autophagy and 'necroapoptophagy'. The concept of 'necroapoptophagy' is presented here as a strategy for varying tissue oxidative stress intensity in ways that induce differential activation of death versus survival programs, resulting in enhanced and sustained representation of healthy functional cells. These strategies are discussed in the context of specialized mesenchymal stromal cells with the potential to synergize with telocytes in stabilizing engrafted progenitor cells, thereby extending periods of healthy life. Information and concepts are summarized in a hypothetical approach to suppressing whole-organism senescence, with methods drawn from emerging understandings of ageing, gained from Cnidarians (jellyfish, corals and anemones) that undergo a unique form of

Progressively sophisticated understanding of cellular and molecular processes that contribute to age-related physical deterioration is being gained from ongoing research into cancer, chronic inflammatory syndromes and other serious disorders that increase with age. Particularly valuable insight has resulted from characterization of how senescent cells affect the tissues in which they form in ways that decrease an organism's overall viability. Increasingly, the underlying pathophysiology of ageing is recognized as a consequence of oxidative damage. This leads to hyperactivity of cell growth pathways, prominently including mTOR (mammalian target of rapamycin), that contribute to a build-up in cells of toxic aggregates such as progerin (a mutant nuclear cytoskeletal protein), lipofuscin and other cellular debris, triggering formation of senescentcellular phenotypes, which interact destructively with surrounding tissue. Indeed, senescent cell ablation dramatically inhibits physical deterioration in progeroid (age-accelerated) mice. This review explores ways in which oxidative stress creates ageing-associated cellular damage and triggers induction of the cell death/survival programs’ apoptosis, necrosis, autophagy and ‘necroapoptophagy’. The concept of ‘necroapoptophagy’ is presented here as a strategy for varying tissue oxidative stress intensity in ways that induce differential activation of death versus survival programs, resulting in enhanced and sustained representation of healthy functional cells. These strategies are discussed in the context of specialized mesenchymal stromal cells with the potential to synergize with telocytes in stabilizing engrafted progenitor cells, thereby extending periods of healthy life. Information and concepts are summarized in a hypothetical approach to suppressing whole-organism senescence, with methods drawn from emerging understandings of ageing, gained from Cnidarians (jellyfish, corals and anemones) that undergo a

Nitric oxide (NO) has been known to preserve the level of chlorophyll (Chl) during leaf senescence. However, the mechanism by which NO regulates Chl breakdown remains unknown. Here we report that NO negatively regulates the activities of Chl catabolic enzymes during dark-induced leaf senescence. The transcriptional levels of the major enzyme genes involving Chl breakdown pathway except for RED CHL CATABOLITE REDUCTASE (RCCR) were dramatically up-regulated during dark-induced Chl degradation in the leaves of Arabidopsis NO-deficient mutant nos1/noa1 that exhibited an early-senescence phenotype. The activity of pheide a oxygenase (PAO) was higher in the dark-induced senescent leaves of nos1/noa1 compared with wild type. Furthermore, the knockout of PAO in nos1/noa1 background led to pheide a accumulation in the double mutant pao1 nos1/noa1, which retained the level of Chl during dark-induced leaf senescence. The accumulated pheide a in darkened leaves of pao1 nos1/noa1 was likely to inhibit the senescence-activated transcriptional levels of Chl catabolic genes as a feed-back inhibitory effect. We also found that NO deficiency led to decrease in the stability of photosynthetic complexes in thylakoid membranes. Importantly, the accumulation of pheide a caused by PAO mutations in combination with NO deficiency had a synergistic effect on the stability loss of thylakoid membrane complexes in the double mutant pao1 nos1/noa1 during dark-induced leaf senescence. Taken together, our findings have demonstrated that NO is a novel negative regulator of Chl catabolic pathway and positively functions in maintaining the stability of thylakoid membranes during leaf senescence. PMID:23418559

Pathogenesis of age-related macular degeneration (AMD), the leading cause of blindness in the world, remains poorly understood. This makes it necessary to create animal models for studying AMD pathogenesis and to design new therapeutic approaches. Here we showed that retinopathy in OXYS rats is similar to human AMD according to clinical signs, morphology, and vascular endothelium growth factor (VEGF) and pigment epithelium-derived factor (PEDF) genes expression. Clinical signs of retinopathy OXYS rats manifest by the age 3 months against the background of significantly reduced expression level of VEGF and PEDF genes due to the decline of the amount of retinal pigment epithelium (RPE) cells and alteration of choroidal microcirculation. The disruption in OXYS rats' retina starts at the age of 20 days and appears as reduce the area of RPE cells but does not affect their ultrastructure. Ultrastructural pathological alterations of RPE as well as develop forms of retinopathy are observed in OXYS rats from age 12 months and manifested as excessive accumulation of lipofuscin in RPE regions adjacent to the rod cells, whirling extentions of the basement membrane into the cytoplasm. These data suggest that primary cellular degenerative alterations in the RPE cells secondarily lead to choriocapillaris atrophy and results in complete loss of photoreceptor cells in the OXYS rats' retina by the age of 24 months. PMID:21191149

With extension of the average lifespan, aging has become a heavy burden in society. Immune senescence is a key risk factor for many age-related diseases such as cancer and increased infections in the elderly, and hence has elicited much attention in recent years. As our body's guardian, the immune system maintains systemic health through removal of pathogens and damage. Autophagy is an important cellular 'clearance' process by which a cell internally delivers damaged organelles and macromolecules to lysosomes for degradation. Here, we discuss the most current knowledge of how impaired autophagy can lead to cellular and immune senescence. We also provide an overview, with examples, of the clinical potential of exploiting autophagy to delay immune senescence and/or rejuvenate immunity to treat various age-related diseases. PMID:27395769

Glycation of apolipoproteins is a major feature of the production of dysfunctional high-density lipoprotein (HDL), which is associated with the incidence of several metabolic diseases such as coronary artery disease and diabetes. In this report, fructated apoA-I (fA-I) induced by fructose treatment showed a covalently multimerized band without cross-linking, and lysine residues were irreversibly modified to prevent crosslinking. Using pancreatic β-cells, insulin secretion was impaired by fA-I in the lipid-free and reconstituted HDL (rHDL) states, by up to 35%, and 40%, respectively, under hyperglycemic conditions (25 mmol/L glucose). Treatment of human umbilical vein endothelial cells (HUVECs) with fA-I and HDL from elderly patients caused a 1.8-fold and 1.5-fold increased cellularsenescence, respectively, along with increased lysosomal enlargement. In the lipid-free and rHDL states, fA-I increased embryo death by 1.5-fold and 2.5-fold, respectively, along with the production of oxidized species. Furthermore, rHDL containing fA-I (fA-I-rHDL) showed a higher isoelectric point (pI, approximately 8.5), whereas rHDL containing nA-I (nA-I-rHDL) showed a narrow band range with lower pI (around 8.0) as well as a much smaller particle size than that of nA-I-rHDL. In conclusion, fructose-mediated apoA-I fructation resulted in the severe loss of several beneficial functions of apoA-I and HDL, including anti-senescence and insulin secretion activities, accompanied with increased susceptibility to protein degradation and structural modification. PMID:27487295

Telomere maintenance is essential for the continued proliferation of dividing cells, and is implicated in chromosome stability and cell immortalization. Telomerase activity allows cells to maintain their telomeric DNA and contributes to the indefinite replicative capacity of cancer cells. Telomerase is expressed in most cancer cells, but not in normal somatic cells, suggesting that telomerase is an attractive target for cancer chemotherapy. Here we screened a chemical library for inhibition of human telomerase, and identified 2,3,7-trichloro-5-nitroquinoxaline (TNQX) as a potent inhibitor. TNQX showed a potent inhibitory effect, with 50% inhibition at approximately 1.4 microM, and did not inhibit DNA and RNA polymerases, including retroviral reverse trancriptase. A series of enzyme kinetic experiments suggested that TNQX is a mixed-type non-competitive inhibitor, with an inhibitor-binding site distinct from the binding sites for the telomeric substrate (TS) primer and the dNTPs. Long-term cultivation of the MCF7 cell line with a drug concentration that did not cause acute cytotoxicity resulted in progressive telomere erosion followed by an increased incidence of chromosome abnormalities and induction of the senescence phenotype. The results presented here indicate that TNQX is a highly potent and selective anti-telomerase agent with good potential for further development as a promising anti-cancer agent. PMID:12689331

Senescence-accelerated mouse prone/8 (SAMP8) mice are known to exhibit age-related deterioration in sleep-wake architecture compared with senescence-accelerated mouse resistant/1 (SAMR1) mice. We investigated whether treatment with Am80 (Tamibarotene), a retinoic acid receptor agonist, would improve sleep in 9-10-month-old SAMP8 mice. One week of Am80 administration improved the decrease in rapid eye movement (REM) sleep shown by SAMP8 mice. Real-time RT-PCR analysis demonstrated an impairment in the hippocampal retinoid cascade (retinoic acid receptor alpha and transthyretin) in SAMP8 in comparison to SAMR1 mice. Am80 treatment induced an increase in mRNA expression in the vesicular acetylcholine transporter in the brainstem and transthyretin in the hippocampus. Furthermore, decreased cortical acetylcholine content in SAMP8 was improved by Am80 administration. Decreased non-REM sleep and delta oscillation were also observed in SAMP8 mice; however, this was not improved by Am80 administration. These results partially support the hypothesis that the effects of aging on sleep-wake architecture are improved by the activation of retinoic acid receptors. The improvement may be induced by the activation of the cholinergic pathway. PMID:20138974

Am80 is a synthetic retinoid that has been used clinically for patients with acute promyelocytic leukemia and has been reported to affect the brain and its neurons. We investigated the influence of Am80 on anti-anxiety-like behavior, which is a characteristic of age-associated emotional disorder, in the P8 strain of senescence-accelerated mice (SAMP8). Am80 at a concentration of 2 mg/kg/day was administered to the mice in their feed for 1.5 months. In open-field and hole-board tests, the number of ambulation, rearing, and head dipping actions, as well as the distance moved were significantly decreased in Am80-treated SAMP8 compared with untreated SAMP8. In the light/dark box test, the latencies for the first exit were significantly increased in the Am80-treated SAMP8 compared with the untreated SAMP8. Immunohistochemical analysis revealed that the area of serotonin transporter-positive immunoreactivity in the coronal sections of the forebrain of the Am80-treated SAMP8 was increased compared with the untreated SAMP8. Furthermore, the metabolic turnovers of serotonin and dopamine were increased in the amygdalae of the SAMP8 by Am80 treatment. Thus, in the present study, Am80 was found to improve exploratory and emotional behavior in SAMP8, suggesting that Am80 regulates monoamines directly or indirectly in this senescence-accelerated model. PMID:23333680

'Cellularsenescence', a term originally defining the characteristics of cultured cells that exceed their replicative limit, has been broadened to describe durable states of proliferative arrest induced by disparate stress factors. Proposed relationships between cellularsenescence, tumour suppression, loss of tissue regenerative capacity and ageing suffer from lack of uniform definition and consistently applied criteria. Here, we highlight caveats in interpreting the importance of suboptimal senescence-associated biomarkers, expressed either alone or in combination. We advocate that more-specific descriptors be substituted for the now broadly applied umbrella term 'senescence' in defining the suite of diverse physiological responses to cellular stress. PMID:26105537

A major goal in cancer and aging research is to discriminate the biochemical modifications that happen locally that could account for the healthiness or malignancy of tissues. Senescence is one general antiproliferative cellular process that acts as a strong barrier for cancer progression, playing a crucial role in aging. Here, we focus on the current methods to assess cellularsenescence, discriminating the advantages and disadvantages of several senescence biomarkers. PMID:22723221

Cellularsenescence permanently arrests the cell division cycle, and has long been thought to prevent the growth of cells at risk for transformation into cancer cells. Four new papers now provide evidence that cellularsenescence indeed limits the development of malignant cancers in mice and humans.

Aging is the main risk factor for many degenerative diseases and declining health. Senescent cells are part of the underlying mechanism for time-dependent tissue dysfunction. These cells can negatively affect neighbouring cells through an altered secretory phenotype: the senescence-associated secretory phenotype (SASP). The SASP induces senescence in healthy cells, promotes tumour formation and progression, and contributes to other age-related diseases such as atherosclerosis, immune-senescence and neurodegeneration. Removal of senescent cells was recently demonstrated to delay age-related degeneration and extend lifespan. To better understand cell aging and to reap the benefits of senescent cell removal, it is necessary to have a reliable biomarker to identify these cells. Following an introduction to cellularsenescence, we discuss several classes of biomarkers in the context of their utility in identifying and/or removing senescent cells from tissues. Although senescence can be induced by a variety of stimuli, senescent cells share some characteristics that enable their identification both in vitro and in vivo. Nevertheless, it may prove difficult to identify a single biomarker capable of distinguishing senescence in all cell types. Therefore, this will not be a comprehensive review of all senescence biomarkers but rather an outlook on technologies and markers that are most suitable to identify and isolate senescent cells. PMID:27212009

Research highlights: {yields} SM22{alpha} overexpression in HepG2 cells leads cells to a growth arrest state, and the treatment of a subclinical dose of {gamma}-radiation or doxorubicin promotes cellularsenescence. {yields} SM22{alpha} overexpression elevates p16{sup INK4a} followed by pRB activation, but there are no effects on p53/p21{sup WAF1/Cip1} pathway. {yields} SM22{alpha}-induced MT-1G activates p16{sup INK4a}/pRB pathway, which promotes cellularsenescence by damaging agents. -- Abstract: Smooth muscle protein 22-alpha (SM22{alpha}) is known as a transformation- and shape change-sensitive actin cross-linking protein found in smooth muscle tissue and fibroblasts; however, its functional role remains uncertain. We reported previously that SM22{alpha} overexpression confers resistance against anti-cancer drugs or radiation via induction of metallothionein (MT) isozymes in HepG2 cells. In this study, we demonstrate that SM22{alpha} overexpression leads cells to a growth arrest state and promotes cellularsenescence caused by treatment with a subclinical dose of {gamma}-radiation (0.05 and 0.1 Gy) or doxorubicin (0.01 and 0.05 {mu}g/ml), compared to control cells. Senescence growth arrest is known to be controlled by p53 phosphorylation/p21{sup WAF1/Cip1} induction or p16{sup INK4a}/retinoblastoma protein (pRB) activation. SM22{alpha} overexpression in HepG2 cells elevated p16{sup INK4a} followed by pRB activation, but did not activate the p53/p21{sup WAF1/Cip1} pathway. Moreover, MT-1G, which is induced by SM22{alpha} overexpression, was involved in the activation of the p16{sup INK4a}/pRB pathway, which led to a growth arrest state and promoted cellularsenescence caused by damaging agents. Our findings provide the first demonstration that SM22{alpha} modulates cellularsenescence caused by damaging agents via regulation of the p16{sup INK4a}/pRB pathway in HepG2 cells and that these effects of SM22{alpha} are partially mediated by MT-1G.

Vascular cell senescence, induced by the DNA damage response or inflammatory stress, contributes to age-associated vascular disease. Using complementary DNA microarray technology, we found that the level of POZ/BTB and AT-hook-containing zinc finger protein 1 (PATZ1) is downregulated during endothelial cell (EC) senescence. PATZ1 may have an important role as a transcriptional repressor in chromatin remodeling and transcription regulation; however, the role of PATZ1 in EC senescence and vascular aging remains unidentified. Knockdown of PATZ1 in young cells accelerated premature EC senescence, which was confirmed by growth arrest, increased p53 protein level and senescence-associated β-galactosidase (SA-β-gal) activity, and repression of EC tube formation. In contrast, overexpression of PATZ1 in senescent cells reversed senescent phenotypes. Cellularsenescence induced by PATZ1 knockdown in young cells was rescued by knockdown of p53, but not by knockdown of p16INK4a. PATZ1 knockdown increased ROS levels, and pretreatment with N-acetylcysteine abolished EC senescence induced by PATZ1 knockdown. Notably, PATZ1 immunoreactivity was lower in ECs of atherosclerotic tissues than those of normal arteries in LDLR−/− mice, and immunoreactivity also decreased in ECs of old human arteries. These results suggest that PATZ1 may have an important role in the regulation of EC senescence through an ROS-mediated p53-dependent pathway and contribute to vascular diseases associated with aging. PMID:22052190

Dysregulation of the cell proliferation has been implicated in the pathophysiology of a number of diseases. Cellularsenescence limits proliferation of cancer cells, preventing tumorigenesis and restricting tissue damage. However, the role of cellularsenescence in proliferative nephritis has not been determined. The proliferative peak in experimental rat nephritis coincided with a peak in E2A expression in the glomeruli. Meanwhile, E12 (an E2A-encoded transcription factor) did not promote proliferation of Mesangial cells (MCs) by itself. We identified caspase-8-binding protein FLICE-associated huge protein (FLASH) as a novel E2A-binding partner by using a yeast two-hybrid screening. Knockdown of FLASH suppressed proliferation of MCs. This inhibitory effect was partially reversed by the knockdown of E2A. In addition, the knockdown of FLASH induced cyclin-dependent kinase inhibitor p21WAF1/CIP1 (p21) expression, but did not affect p53 expression. Furthermore, overexpression of E12 and E47 induced p21, but not p53 in MCs, in the absence of FLASH. We also demonstrated that E2A and p21 expression at the peak of proliferation was followed by significant induction of FLASH in mesangial areas in rat proliferative glomerulonephritis. Moreover, we revealed that FLASH negatively regulates cellularsenescence via the interaction with E12. We also demonstrated that FLASH is involved in the TNF-α-induced p21 expressions. These results suggest that the functional interaction of E2A and FLASH play an important role in cell proliferation and cellularsenescence via regulation of p21 expression in experimental glomerulonephritis. PMID:26208142

Cellularsenescence is a cell cycle arrest accompanied by high expression of cyclin dependent kinase inhibitors which counteract overactive growth signals, which serves as a tumor suppressive mechanism. Senescence can be a result of telomere shortening (natural or replicative senescence) or DNA damage resulting from exogenous stressors (induced senescence). Here, we performed gene expression profiling through RNA-seq of replicative senescence, adriamycin-induced senescence, H2O2-induced senescence, and 5-aza-2-deoxycytidine-induced senescence in order to profile the pathways controlling various types of senescence. Overall, the pathways common to all 4 types of senescence were related to inflammation and the innate immune system. It was also evident that 5-aza-induced senescence mirrors natural replicative senescence due to telomere shortening. We also examined the prevalence of senescence-associated secretory phenotype (SASP) factors in the RNA-seq data, showing that it is a common characteristic of all 4 types of senescence. In addition, we could discriminate changes in gene expression due to quiescence during cellularsenescence from those that were specific to senescence. PMID:25483067

The senescent phenotype was first described in 1961 as a phenomenon characterized by the cessation of cellular division. After years of debate as to whether it represented a tissue culture artifact or an important biological process, it is now appreciated that senescence plays an important role in tumorigenesis. Further, senescence is integral to normal biological processes such as embryogenesis and the maintenance of tissue homeostasis. Now with defined roles in development, wound healing, tumor promotion and tumor suppression, it is not surprising that attention has turned to refining our understanding of the mechanisms behind, and consequences of, the induction of senescence. One emerging role for senescence lies in the ability of senescence to orchestrate an inflammatory response: factors secreted by senescent cells have been identified in multiple contexts to modulate various aspects of the immune response. As with many of the previously described roles for senescence, the type of inflammation established by the senescence phenotype is varied and dependent on context. In this review, we discuss the current state of the field with a focus on the paradoxical outcomes of the senescence-induced inflammatory responses in the context of cancer. A more complete understanding of senescence and an appreciation for its complexities will be important for eventual development of senescence-targeted therapies. PMID:26453912

The widespread environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent toxicant that causes significant neurotoxicity. However, the biological events that participate in this process remain largely elusive. In the present study, we demonstrated that TCDD exposure triggered apparent premature senescence in rat pheochromocytoma (PC12) and human neuroblastoma SH-SY5Y cells. Senescence-associated β-galactosidase (SA-β-Gal) assay revealed that TCDD induced senescence in PC12 neuronal cells at doses as low as 10 nM. TCDD led to F-actin reorganization and the appearance of an alternative senescence marker, γ-H2AX foci, both of which are important features of cellularsenescence. In addition, TCDD exposure altered the expression of senescence marker proteins, such as p16, p21 and p-Rb, in both dose- and time-dependent manners. Furthermore, we demonstrated that TCDD promotes mitochondrial dysfunction and the accumulation of cellular reactive oxygen species (ROS) in PC12 cells, leading to the activation of signaling pathways that are involved in ROS metabolism and senescence. TCDD-induced ROS generation promoted significant oxidative DNA damage and lipid peroxidation. Notably, treatment with the ROS scavenger N-acetylcysteine (NAC) markedly attenuated TCDD-induced ROS production, cellular oxidative damage and neuronal senescence. Moreover, we found that TCDD induced a similar ROS-mediated senescence response in human neuroblastoma SH-SY5Y cells. In sum, these results demonstrate for the first time that TCDD induces premature senescence in neuronal cells by promoting intracellular ROS production, supporting the idea that accelerating the onset of neuronal senescence may be an important mechanism underlying TCDD-induced neurotoxic effects. PMID:24587053

The widespread environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent toxicant that causes significant neurotoxicity. However, the biological events that participate in this process remain largely elusive. In the present study, we demonstrated that TCDD exposure triggered apparent premature senescence in rat pheochromocytoma (PC12) and human neuroblastoma SH-SY5Y cells. Senescence-associated β-galactosidase (SA-β-Gal) assay revealed that TCDD induced senescence in PC12 neuronal cells at doses as low as 10 nM. TCDD led to F-actin reorganization and the appearance of an alternative senescence marker, γ-H2AX foci, both of which are important features of cellularsenescence. In addition, TCDD exposure altered the expression of senescence marker proteins, such as p16, p21 and p-Rb, in both dose- and time-dependent manners. Furthermore, we demonstrated that TCDD promotes mitochondrial dysfunction and the accumulation of cellular reactive oxygen species (ROS) in PC12 cells, leading to the activation of signaling pathways that are involved in ROS metabolism and senescence. TCDD-induced ROS generation promoted significant oxidative DNA damage and lipid peroxidation. Notably, treatment with the ROS scavenger N-acetylcysteine (NAC) markedly attenuated TCDD-induced ROS production, cellular oxidative damage and neuronal senescence. Moreover, we found that TCDD induced a similar ROS-mediated senescence response in human neuroblastoma SH-SY5Y cells. In sum, these results demonstrate for the first time that TCDD induces premature senescence in neuronal cells by promoting intracellular ROS production, supporting the idea that accelerating the onset of neuronal senescence may be an important mechanism underlying TCDD-induced neurotoxic effects. PMID:24587053

New and stimulating results have challenged the concept that cellularsenescence might not be synonymous with aging. It is indisputable that during aging, senescent cell accumulation has an impact on organismal health. Nevertheless, senescent cells are now known to display physiological roles during embryonic development, during wound healing repair and as a cellular response to stress. The fact that senescence has been found in cells that did not attain their maximal round of replications, nor have metabolic alterations or DNA damage, also challenges the paradigm that senescence is cellular aging, and it is in favor of the idea that cellularsenescence is a phenomenon that has a function by itself. Therefore, in order to understand this phenomenon it is important to analyze the relationship between senescence and other cellular responses that have many features in common, such as apoptosis, cancer and autophagy, particularly highlighting their role during development and adulthood. PMID:27059850

Background: Amyloid β (Aβ) has been established as a key factor for the pathological changes in the brains of patients with Alzheimer's disease (AD), and cellularsenescence is closely associated with aging and cognitive impairment. However, it remains blurred whether, in the AD brains, Aβ accelerates the neuronal senescence and whether this senescence, in turn, impairs the cognitive function. This study aimed to explore the expression of senescence-associated genes in the hippocampal tissue from young to aged 5XFAD mice and their age-matched wild type (WT) mice to determine whether senescent neurons are present in the transgenic AD mouse model. Methods: The 5XFAD mice and age-matched wild type mice, both raised from 1 to 18 months, were enrolled in the study. The senescence-associated genes in the hippocampus were analyzed and differentially expressed genes (DEGs) were screened by quantitative real-time polymerase chain reaction. Cognitive performance of the mice was evaluated by Y-maze and Morris water maze tests. Oligomeric Aβ (oAβ) (1–42) was applied to culture primary neurons to simulate the in vivo manifestation. Aging-related proteins were detected by Western blotting analysis and immunofluorescence. Results: In 5XFAD mice, of all the DEGs, the senescence-associated marker p16 was most significantly increased, even at the early age. It was mainly localized in neurons, with a marginal expression in astrocytes (labeled as glutamine synthetase), nil expression in activated microglia (labeled as Iba1), and negatively correlated with the spatial cognitive impairments of 5XFAD mice. oAβ (1–42) induced the production of senescence-related protein p16, but not p53 in vitro, which was in line with the in vivo manifestation. Conclusions: oAβ-accelerated neuronal senescence may be associated with the cognitive impairment in 5XFAD mice. Senescence-associated marker p16 can serve as an indicator to estimate the cognitive prognosis for AD population. PMID

The sigma1 receptor is a unique intracellular receptor whose activation results in an efficient modulation of several neurotransmitter responses. Its role as a target for the rapid nongenomic effects of neuro(active)steroids and the age-related diminutions in steroid levels suggested that targeting the sigma1 receptor might allow alleviation of age-related neuronal dysfunctions. We examined here the expression and behavioral efficacy of sigma1 receptors in the senescence-accelerated (SAM) mouse model. The sigma1 receptor mRNA expression was measured by using comparative RT-PCR in the olfactory bulb, hippocampus, hypothalamus, cortex, or cerebellum of senescence-prone SAMP/8 and senescence-resistant SAMR/1 control animals. No difference was observed between substrains in 6-, 9-, and 12-month-old (m.o.) mice. The sigma1 protein expression was analyzed by using immunohistochemical techniques. Labeling was intense in the olfactory bulb, hippocampus, hypothalamus, and midbrain of both SAMR/1 and SAMP/8 mice, and the distribution appeared unchanged in 6-, 9-, and 12-m.o. animals. The receptor's in vivo availability was examined by using in vivo [3H](+)-SKF-10,047 binding. No age-related difference was observed in the olfactory bulb, hippocampus, hypothalamus, cortex, cerebellum, and brainstem of 6- or 12-m.o. SAMR/1 or SAMP/8 mice. The antidepressant efficacy of the selective agonist igmesine was examined in the forced-swimming test. The compound decreased significantly the immobility duration at 60 mg/kg in 6- and 12-m.o. SAMR/1 and in 6-m.o. SAMP/8 mice. In 12-m.o. SAMP/8 mice, the drug efficacy was facilitated; a significant effect was measured at 30 mg/kg. Decreased neurosteroid levels, particularly of progesterone, were seen in 12-m.o. SAMP/8 mice that might explain the enhanced efficacy of igmesine. Preserved sigma1 receptor expression and enhanced behavioral efficacy of sigma1 agonists were measured in SAM animals, confirming the therapeutic opportunities for

The aim of this study was to investigate the role of macrophage polarization in aging heart. Macrophage differentiation is pathogenically linked to many inflammatory and immune disorders. It is often preceded by myocardial inflammation, which is characterized by increased cardiac damage and pro-inflammatory cytokine levels. Therefore, we investigated the hypothesis that senescenceaccelerated-prone (SAMP8) mice cardiac tissue would develop macrophage polarization compared with senescence-resistant control (SAMR1) mice. Both SAMP8 and SAMR1 mice were sacrificed when they became six month old. We evaluated, histo-pathological changes and modifications in protein expression by Western blotting and immuno-histochemical staining for M1 and M2 macrophage markers, high mobility group protein (HMG)B1 and its cascade proteins, pro-inflammatory factors and inflammatory cytokines in cardiac tissue. We observed significant upregulation of HMGB1, toll-like receptor (TLR)2, TLR4, nuclear factor (NF)κB p65, tumor necrosis factor (TNF)α, cyclooxygenase (COX)2, interferon (IFN)γ, interleukin (IL)-1β, IL-6 and M1 like macrophage specific marker cluster of differentiation (CD)68 expressions in SAMP8 heart. In contrast, M2 macrophage specific marker CD36, and IL-10 expressions were down-regulated in SAMP8 mice. The results from the study demonstrated that, HMGB1-TLR2/TLR4 signaling cascade and induction of phenotypic switching to M1 macrophage polarization in SAMP8 mice heart would be one of the possible reasons behind the cardiac dysfunction and thus it could become an important therapeutic target to improve the age related cardiac dysfunction. PMID:27070323

Cellularsenescence is currently viewed as a response to DNA damage. In this report, we showed that non-damaging agents such as sodium butyrate-induced p21 and ectopic expression of either p21 or p16 cause cellularsenescence without detectable DNA breaks. Nevertheless, senescent cells displayed components of DNA damage response (DDR) such as γH2AX foci and uniform nuclear staining for p-ATM. Importantly, there was no accumulation of 53BP1 in γH2AX foci of senescent cells. Consistently, comet assay failed to detect DNA damage. Rapamycin, an inhibitor of mTOR, which was shown to suppress cellularsenescence, decreased γH2AX foci formation. Thus, cellularsenescence leads to activation of atypical DDR without detectable DNA damage. Pseudo-DDR may be a marker of general over-activation of senescent cells. PMID:19946210

Cellularsenescence is described to be a consequence of telomere erosion during the replicative life span of primary human cells. Quiescence should therefore not contribute to cellular aging but rather extend lifespan. Here we tested this hypothesis and demonstrate that cultured long-term quiescent human fibroblasts transit into senescence due to similar cellular mechanisms with similar dynamics and with a similar maximum life span as proliferating controls, even under physiological oxygen conditions. Both, long-term quiescent and senescent fibroblasts almost completely fail to undergo apoptosis. The transition of long-term quiescent fibroblasts into senescence is also independent of HES1 which protects short-term quiescent cells from becoming senescent. Most significantly, DNA damage accumulates during senescence as well as during long-term quiescence at physiological oxygen levels. We suggest that telomere-independent, potentially maintenance driven gradual induction of cellularsenescence during quiescence is a counterbalance to tumor development. PMID:25531649

Senescenceaccelerated mouse-prone (SAMP) mice with a shortened life span show accelerated changes in many of the signs of aging and a shorter reproductive life span than SAM-resistant (SAMR) controls. We previously showed that functional regression (progesterone dissimilation) occurs in abnormally accumulated luteal bodies (aaLBs) of SAMP mice, but structural regression of luteal cells in aaLB is inhibited. A deficiency of luteal cell apoptosis causes the abnormal accumulation of LBs in SAMP ovaries. In the present study, to show the abnormality of Fas ligand (FasL)/Fas-mediated apoptosis signal transducing factors in the aaLBs of the SAMP ovaries, we assessed the changes in the expression of FasL, Fas, caspase-8 and caspase-3 mRNAs by reverse transcription-polymerase chain reaction, and in the expression and localization of FasL, Fas and activated caspase-3 proteins by Western blotting and immunohistochemistry, respectively, during the estrus cycle/luteolysis. These mRNAs and proteins were expressed in normal LBs of both SAMP and SAMR ovaries, but not at all or only in trace amounts in aaLBs of SAMP, indicating that structural regression is inhibited by blockage of the expression of these transducing factors in luteal cells of aaLBs in SAMP mice. PMID:14967896

The senescence-accelerated mouse (SAM) is an accelerated aging model that was established through phenotypic selection from a common genetic pool of AKR/J strain of mice. The SAM model was established in 1981, including nine major senescence-accelerated mouse prone (SAMP) substrains and three major senescence-accelerated mouse resistant (SAMR) substrains, each of which exhibits characteristic disorders. Recently, SAMP8 have drawn attention in gerontological research due to its characteristic learning and memory deficits at old age. Many recent reports provide insight into mechanisms of the cognitive impairment and pathological changes in SAMP8. Therefore, this mini review examines the recent findings of SAMP8 mice abnormalities at the gene and protein levels. The genes and proteins described in this review are functionally categorized into neuroprotection, signal transduction, protein folding/degradation, cytoskeleton/transport, immune response and reactive oxygen species (ROS) production. All of these processes are involved in learning and memory. Although these studies provide insight into the mechanisms that contribute to the learning and memory decline in aged SAMP8 mice, higher throughput techniques of proteomics and genomics are necessary to study the alterations of gene expression and protein abnormalities in SAMP8 mice brain in order to more completely understand the central nervous system dysfunction in this mouse model. The SAMP8 is a good animal model to investigate the fundamental mechanisms of age-related learning and memory deficits at the gene and protein levels. PMID:16026957

The senescence-accelerated mouse prone10 (SAMP10) strain, a model of aging, exhibits cognitive impairments and cerebral atrophy. We noticed that SAMP10/TaSlc mice, a SAMP10 substrain, have developed persistent glucosuria over the past few years. In the present study, we characterized SAMP10/TaSlc mice and further identified a spontaneous mutation in the Slc5a2 gene encoding sodium-glucose co-transporter (SGLT) 2. The mean concentration of urine glucose was high in SAMP10/TaSlc mice and increased further with advancing age, whereas other strains of senescence-accelerated mice, including SAMP1/SkuSlc, SAMP6/TaSlc and SAMP8/TaSlc or normal aging control SAMR1/TaSlc mice, exhibited no detectable glucose in urine. SAMP10/TaSlc mice consumed increasing amounts of food and water compared to SAMR1/TaSlc mice, suggesting the compensation of polyuria and the loss of glucose. Oral glucose tolerance tests showed decreased glucose reabsorption in the kidney of SAMP10/TaSlc mice. In addition, blood glucose levels decreased in an age-dependent fashion. The kidney was innately larger than that of control mice with no histological alterations. We examined the expression levels of glucose transporters in the kidney. Among SGLT1, SGLT2, glucose transporter (GLUT) 1 and GLUT2, we found a significant decrease only in the level of SGLT2. DNA sequencing of SGLT2 in SAMP10/TaSlc mice revealed a single nucleotide deletion of guanine at 1236, which resulted in a frameshift mutation that produced a truncated protein. We designate this strain as SAMP10/TaSlc-Slc5a2(slc) (SAMP10-ΔSglt2). Recently, SGLT2 inhibitors have been demonstrated to be effective for the treatment of patients with type 2 diabetes (T2D). SAMP10-ΔSglt2 mice may serve as a unique preclinical model to study the link between aging-related neurodegenerative disorders and T2D. PMID:25450362

Cellularsenescence suppresses cancer by arresting cell proliferation, essentially permanently, in response to oncogenic stimuli, including genotoxic stress. We modified the use of antibody arrays to provide a quantitative assessment of factors secreted by senescent cells. We show that human cells induced to senesce by genotoxic stress secrete myriad factors associated with inflammation and malignancy. This senescence-associated secretory phenotype (SASP) developed slowly over several days and only after DNA damage of sufficient magnitude to induce senescence. Remarkably similar SASPs developed in normal fibroblasts, normal epithelial cells, and epithelial tumor cells after genotoxic stress in culture, and in epithelial tumor cells in vivo after treatment of prostate cancer patients with DNA-damaging chemotherapy. In cultured premalignant epithelial cells, SASPs induced an epithelial-mesenchyme transition and invasiveness, hallmarks of malignancy, by a paracrine mechanism that depended largely on the SASP factors interleukin (IL)-6 and IL-8. Strikingly, two manipulations markedly amplified, and accelerated development of, the SASPs: oncogenic RAS expression, which causes genotoxic stress and senescence in normal cells, and functional loss of the p53 tumor suppressor protein. Both loss of p53 and gain of oncogenic RAS also exacerbated the promalignant paracrine activities of the SASPs. Our findings define a central feature of genotoxic stress-induced senescence. Moreover, they suggest a cell-nonautonomous mechanism by which p53 can restrain, and oncogenic RAS can promote, the development of age-related cancer by altering the tissue microenvironment.

AMPK activation is beneficial for cellular homeostasis and senescence prevention. However, the molecular events involved in AMPK activation are not well defined. In this study, we addressed the mechanism underlying the protective effect of AMPK on oxidative stress-induced senescence. The results showed that AMPK was inactivated in senescent cells. However, pharmacological activation of AMPK by metformin and berberine significantly prevented the development of senescence and, accordingly, inhibition of AMPK by Compound C was accelerated. Importantly, AMPK activation prevented hydrogen peroxide-induced impairment of the autophagic flux in senescent cells, evidenced by the decreased p62 degradation, GFP-RFP-LC3 cancellation, and activity of lysosomal hydrolases. We also found that AMPK activation restored the NAD(+) levels in the senescent cells via a mechanism involving mostly the salvage pathway for NAD(+) synthesis. In addition, the mechanistic relationship of autophagic flux and NAD(+) synthesis and the involvement of mTOR and Sirt1 activities were assessed. In summary, our results suggest that AMPK prevents oxidative stress-induced senescence by improving autophagic flux and NAD(+) homeostasis. This study provides a new insight for exploring the mechanisms of aging, autophagy and NAD(+) homeostasis, and it is also valuable in the development of innovative strategies to combat aging. PMID:26890602

Memantine is a N-methyl-D-aspartate (NMDA) receptor antagonist approved for the treatment of moderate to severe Alzheimer's disease (AD). Environmental enrichment (EE) has shown significant beneficial effects on functional improvement in AD. In this study, we sought to determine whether combining these two distinct therapies would yield greater benefit than either drug used alone. We investigated the effect of memantine combined with EE on spatial learning and memory and AD-like pathology in a widely used AD model, the senescence-accelerated prone mice (SAMP8). The SAMP8 mice were randomly assigned to enriched housing (EH) or standard housing (SH), where either memantine (20 mg/kg) or saline was given by gastric lavage once daily continuously for eight weeks. Our results showed that, when provided separately, memantine and EE significantly improved spatial learning and memory by shortening escape latencies and increasing the frequency of entrance into the target quadrant. When combined, memantine and EE showed additive effect on learning and memory as evidenced by significant shorter escape latencies and higher frequency of target entrance than either drug alone. Consistent with the behavior results, pathological studies showed that both memantine and EE significantly reduced hippocampal CA1 neurofibrilliary tangles (NFTs) as well as amyloid beta precursor protein (APP) levels. Combining both therapies synergistically lessened NFTs and APP expression compared to either drug alone in SAMP8 mice, indicating that the combination of memantine with EE could offer a novel and efficient therapeutic strategy for the treatment of AD. PMID:23554783

This study examines the cellular automata traffic flow model, which considers the heterogeneity of vehicle acceleration and the delay probability of vehicles. Computer simulations are used to identify three typical phases in the model: free-flow, synchronized flow, and wide moving traffic jam. In the synchronized flow region of the fundamental diagram, the low and high velocity vehicles compete with each other and play an important role in the evolution of the system. The analysis shows that there are two types of bistable phases. However, in the original Nagel and Schreckenberg cellular automata traffic model, there are only two kinds of traffic conditions, namely, free-flow and traffic jams. The synchronized flow phase and bistable phase have not been found.

Most cells cannot divide indefinitely due to a processtermed cellular or replicative senescence. Replicative senescence appearsto be a fundamental feature of somatic cells, with the exception of mosttumour cells and possibly certain stem cells. How do cells sense thenumber of divisions they have completed? Although it has not yet beencritically tested, the telomere shortening hypothesis is currentlyperhaps the best explanation for a cell division 'counting' mechanism.Why do cells irreversibly cease proliferation after completing a finitenumber of divisions? It is now known that replicative senescence altersthe expression of a few crucial growth-regulatory genes. It is not knownhow these changes in growth-regulatory gene expression are related totelomere shortening in higher eukaryotes. However, lower eukaryotes haveprovided several plausible mechanisms. Finally, what are thephysiological consequences of replicative senescence? Several lines ofevidence suggest that, at least in human cells, replicative senescence isa powerful tumour suppressive mechanism. There is also indirect evidencethat replicative senescence contributes to ageing. Taken together,current findings suggest that, at least in mammals, replicativesenescence may have evolved to curtail tumorigenesis, but may also havethe unselected effect of contributing to age-related pathologies,including cancer.

Bone marrow-derived cells enter the brain in a non-inflammatory condition through the attachments of choroid plexus and differentiate into ramified myeloid cells. Neurodegenerative conditions may be associated with altered immune-brain interaction. The senescence-accelerated mouse prone 10 (SAMP10) undergoes earlier onset neurodegeneration than C57BL/6 (B6) strain. We hypothesized that the dynamics of immune cells migrating from the bone marrow to the brain is perturbed in SAMP10 mice. We created 4 groups of radiation chimeras by intra-bone marrow-bone marrow transplantation using 2-month-old (2 mo) and 10 mo SAMP10 and B6 mice as recipients with GFP transgenic B6 mice as donors, and analyzed histologically 4 months later. In the [B6 → 10 mo SAMP10] chimeras, more ramified marrow-derived cells populated a larger number of discrete brain regions than the other chimeras, especially in the diencephalon. Multiplex cytokine assays of the diencephalon prepared from non-treated 3 mo and 12 mo SAMP10 and B6 mice revealed that 12 mo SAMP10 mice exhibited higher tissue concentrations of CXCL1, CCL11, G-CSF, CXCL10 and IL-6 than the other groups. Immunohistologically, choroid plexus epithelium and ependyma produced CXCL1, while astrocytic processes in the attachments of choroid plexus expressed CCL11 and G-CSF. The median eminence produced CXCL10, hypothalamic neurons G-CSF and tanycytes CCL11 and G-CSF. These brain cytokine profile changes in 12 mo SAMP10 mice were likely to contribute to acceleration of the dynamics of marrow-derived cells to the diencephalon. Further studies on the functions of ramified marrow-derived myeloid cells would enhance our understanding of the brain-bone marrow interaction. PMID:25577138

Aging-related vascular dysfunction contributes to cardiovascular morbidity and mortality. Cartilage oligomeric matrix protein (COMP), a vascular extracellular matrix protein, has been described as a negative regulatory factor for the vascular aging-related processes including atherosclerosis and vascular calcification. However, whether COMP is implicated in the process of vascular aging remains unclear. Here, we identified a novel function of COMP in preventing vascular aging and vascular smooth muscle cells (VSMCs) senescence. Firstly, vascular COMP expression was decreased in three different senescence-accelerated mouse models and was also declining with age. COMP(-/-) mice displayed elevated senescence-associated markers expression, including p53, p21 and p16, in the aortas compared with their wild type (WT) littermates. In accordance, COMP deficiency induced aging-related vascular dysfunction as evidenced by the significantly reduced phenylephrine-induced contraction and increased vascular stiffness as evaluated by pulse wave velocity. The aortic wall of COMP(-/-) mice was susceptible to senescence by displaying senescence-associated β-galactosidase (SA β-gal) activity induced by periadventitial application of CaCl2 to the abdominal aorta. In vitro, COMP knockdown by small interfering (si) RNA led to the elevation of p53, p21 and p16 as well as SA β-gal activity in VSMCs after H2O2 stimulation. VSMCs isolated from COMP(-/-) mice showed elevated senescence-associated markers expression and supplement of COMP adenovirus to COMP-deficient VSMCs greatly rescued cellularsenescence. Taken together, these findings revealed the essential role of COMP in retarding the development of vascular aging and VSMC senescence. PMID:27498005

Long-term consumption of artificial sweeteners (AS) has been the recent focus of safety concerns. However, the potential risk of the AS in cardiovascular disease and lipoprotein metabolism has not been investigated sufficiently. We compared the influence of AS (aspartame, acesulfame K, and saccharin) and fructose in terms of functional and structural correlations of apolipoprotein (apo) A-I and high-density lipoproteins (HDL), which have atheroprotective effects. Long-term treatment of apoA-I with the sweetener at physiological concentration (3 mM for 168 h) resulted in loss of antioxidant and phospholipid binding activities with modification of secondary structure. The AS treated apoA-I exhibited proteolytic cleavage to produce 26 kDa-fragment. They showed pro-atherogenic properties in acetylated LDL phagocytosis of macrophages. Each sweetener alone or sweetener-treated apoA-I caused acceleratedsenescence in human dermal fibroblasts. These results suggest that long-term consumption of AS might accelerate atherosclerosis and senescence via impairment of function and structure of apoA-I and HDL. PMID:21533907

Long-term consumption of artificial sweeteners (AS) has been the recent focus of safety concerns. However, the potential risk of the AS in cardiovascular disease and lipoprotein metabolism has not been investigated sufficiently. We compared the influence of AS (aspartame, acesulfame K, and saccharin) and fructose in terms of functional and structural correlations of apolipoprotein (apo) A-I and high-density lipoproteins (HDL), which have atheroprotective effects. Long-term treatment of apoA-I with the sweetener at physiological concentration (3 mM for 168 h) resulted in loss of antioxidant and phospholipid binding activities with modification of secondary structure. The AS treated apoA-I exhibited proteolytic cleavage to produce 26 kDa-fragment. They showed pro-atherogenic properties in acetylated LDL phagocytosis of macrophages. Each sweetener alone or sweetener-treated apoA-I caused acceleratedsenescence in human dermal fibroblasts. These results suggest that long-term consumption of AS might accelerate atherosclerosis and senescence via impairment of function and structure of apoA-I and HDL. PMID:21533907

Senescence-accelerated mice (SAMP8) serve as a model for Alzheimer's disease (AD) as they exhibit early loss of memory and increased amyloid precursor protein (APP) expression. APP is a ubiquitous membrane protein that is physiologically processed by site-specific proteolysis firstly by alpha- or beta-secretases, releasing a large fragment called APP(S) that contains most of the extracellular sequences of APP, a small extracellular stub, the transmembrane region and the cytoplasmic tail of APP (;AICD'-APP intracellular domain). These are subsequently cleaved by gamma-secretase at multiple sites in the transmembrane region, releasing small peptides, Abeta(1-40) and Abeta(1-42), the major components of AD-associated amyloid fibrils. gamma-secretase is a high-molecular-mass complex composed of presenilin-1 (PS1), nicastrin, APH-1 and Pen-2. As PS1 has been shown to play a critical role in facilitating gamma-secretase activity, and mutations in this protein are associated with familial AD (FAD), we have cloned it from SAMP8 mouse hippocampus and compared its sequence with those of other species. Furthermore, changes in the expression of PS1 with age in the hippocampal tissue of SAMP8 were studied. The results showed that the SAMP8 PS1 cDNA sequence is identical to that of normal mice. However, its expression in the hippocampus of SAMP8 exhibited an increase, while CD-1 mice, a strain that does not exhibit premature memory loss, showed no change with age. An increased amount or mutation(s) in PS1, which alters the stoichiometric balance of the gamma-secretase complex, may be the cause of aberrant or increased processing of APP, resulting in Abeta accumulation leading to loss of memory. PMID:19181896

Clinical studies using omega-3 polyunsaturated fatty acids (ω3-PUFA) to Crohn's disease (CD) are conflicting. Beneficial effects of dietary ω3-PUFA intake in various experimental inflammatory bowel disease (IBD) models have been reported. However, animal models of large intestinal inflammation have been used in all previous studies, and the effect of ω3 fat in an animal model of small intestinal inflammation has not been reported. We hypothesized that the effects of ω3 fat are different between large and small intestine. The aim of this study was to determine whether the direct effect of ω3 fat is beneficial for small intestinal inflammation. Senescenceaccelerated mice (SAM)P1/Yit mice showed remarkable inflammation of the terminal ileum spontaneously. The numbers of F4/80-positive monocyte–macrophage cells as well as β7-integrin-positive lymphocytes in the intestinal mucosa were increased significantly compared with those in the control mice (AKR-J mice). The area of mucosal addressin cell adhesion molecule-1 (MAdCAM-1)-positive vessels was also increased. The degree of expression levels of monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-6 and interferon (IFN)-γ mRNA were increased significantly compared with those in the control mice. The feeding of two different kinds of ω3 fat (fish-oil-rich and perilla-oil-rich diets) for 16 weeks to SAMP1/Yit mice ameliorated inflammation of the terminal ileum significantly. In both the ω3-fat-rich diet groups, enhanced infiltration of F4/80-positive monocytes/macrophages in intestinal mucosa of SAMP1/Yit mice cells and the increased levels of MCP-1, IL-6 and IFN-γ mRNA expression were ameliorated significantly compared with those in the control diet group. The results suggest that ω3 fat is beneficial for small intestinal inflammation by inhibition of monocyte recruitment to inflamed intestinal mucosa. PMID:19793338

Vitamin K2 (VK2) has been used as a therapeutic agent for osteoporosis, since it has been suggested to be able to reduce the frequency of fractures by improving bone quality; however, bone turnover is strictly regulated by various cytokines and hormones. In the present study, the effect of menaquinone-4 (MK-4) on bone turnover was investigated using the senescence-accelerated mouse prone 6 (SAMP6) strain. Since water-immersion restraint stress (WRS) causes a significant decrease in bone mineral density (BMD), WRS was used as the bone resorption model in the SAMP6 strain. Six-week-old SAMP6 male mice were divided into the following three groups: Control, WRS and WRS + MK-4. WRS was performed for 6 h per day, 5 times a week, for 4 weeks. Following WRS, MK-4 (30 mg/kg) was injected subcutaneously 3 times a week for 4 weeks. No growth retardation was observed in the WRS groups as compared with the control group. In the WRS groups, the BMD was significantly lower than that in the control group. The levels of bone formation and resorption markers were increased in the WRS groups, indicating that WRS reduced the BMD by promoting high bone turnover. A bone histomorphometrical examination showed that the trabecular (Tb) bone mass in the secondary spongiosa at the distal femur was significantly reduced in the WRS mice, and this reduction was abrogated by MK-4 treatment. Specifically, the Tb bone reduction was caused by the activation of osteoclasts (Ocs), and Oc activity was suppressed by MK-4. The number of osteoblasts and the mineral apposition rate were significantly increased in the WRS and WRS + MK-4 mice, suggesting that WRS triggered a significantly higher mineral apposition rate. These results indicate that MK-4 can induce recovery from the bone mineral loss caused by WRS treatment. Further studies are required to clarify the association between bone quality and MK-4. PMID:26622403

Sarcopenia-related falls and fall-related injuries in community-dwelling elderly people garnered more and more interest in recent years. Low-magnitude high-frequency vibration (LMHFV) was proven beneficial to musculoskeletal system and recommended for sarcopenia treatment. This study aimed to evaluate the effects of LMHFV on the sarcopenic animals and explore the mechanism of the stimulatory effects. Senescence-accelerated mouse P8 (SAMP8) mice at month 6 were randomized into control (Ctrl) and vibration (Vib) groups and the mice in the Vib group were given LMHFV (0.3 g, 20 min/day, 5 days/week) treatment. At months 0, 1, 2, 3, and 4 post-treatment, muscle mass, structure, and function were assessed. The potential proliferation capacity of the muscle was also evaluated by investigating satellite cells (SCs) pool and serum myostatin expression. At late stage, the mice in the Vib group showed higher muscle strength (month 4, p = 0.028). Generally, contractibility was significantly improved by LMHFV (contraction time [CT], p = 0.000; half-relaxation time [RT50], p = 0.000). Enlarged cross-sectional area of fiber type IIA was observed in the Vib group when compared with Ctrl group (p = 0.000). No significant difference of muscle mass was observed. The promotive effect of LMHFV on myoregeneration was reflected by suppressed SC pool reduction (month 3, p = 0.000; month 4, p = 0.000) and low myostatin expression (p = 0.052). LMHFV significantly improved the structural and functional outcomes of the skeletal muscle, hence retarding the progress of sarcopenia in SAMP8. It would be a good recommendation for prevention of the diseases related to skeletal muscle atrophy. PMID:26608404

Harboring the behavioral and histopathological signatures of Alzheimer's disease (AD), senescenceaccelerated mouse-prone 8 (SAMP8) mice are currently considered a robust model for studying AD. However, the underlying mechanisms, prioritized pathways and genes in SAMP8 mice linked to AD remain unclear. In this study, we provide a biological interpretation of the molecular underpinnings of SAMP8 mice. Our results were derived from differentially expressed genes in the hippocampus and cerebral cortex of SAMP8 mice compared to age-matched SAMR1 mice at 2, 6, and 12 months of age using cDNA microarray analysis. On the basis of PPI, MetaCore and the co-expression network, we constructed a distinct genetic sub-network in the brains of SAMP8 mice. Next, we determined that the regulation of synaptic transmission and apoptosis were disrupted in the brains of SAMP8 mice. We found abnormal gene expression of RAF1, MAPT, PTGS2, CDKN2A, CAMK2A, NTRK2, AGER, ADRBK1, MCM3AP, and STUB1, which may have initiated the dysfunction of biological processes in the brains of SAMP8 mice. Specifically, we found microRNAs, including miR-20a, miR-17, miR-34a, miR-155, miR-18a, miR-22, miR-26a, miR-101, miR-106b, and miR-125b, that might regulate the expression of nodes in the sub-network. Taken together, these results provide new insights into the biological and genetic mechanisms of SAMP8 mice and add an important dimension to our understanding of the neuro-pathogenesis in SAMP8 mice from a systems perspective. PMID:24194717

Cellularsenescence plays an important role in diverse biological processes such as tumorigenesis and organismal aging. However, lack of methods to specifically identify and isolate live senescent cells hampers the precise understanding of the molecular mechanisms regulating cellularsenescence. Here, we report that utilization of fluorescent ubiquitination-based cell cycle indicator (FUCCI) technology allows isolation of live premature senescent cells induced by doxorubicin treatment. Exposure of human foreskin fibroblasts (HFFs) to a low dose of doxorubicin led to cellularsenescent phenotypes including formation of γ-H2AX and 53BP1 foci indicative of DNA damage, decreased cell proliferation and increased senescence-associated β-galactosidase (SA-β-gal) activity. Importantly, doxorubicin-induced senescent cells were arrested at S/G2/M phases of cell cycle which can be reported by a construct encoding a fragment of hGeminin fused with monomeric Azami-Green (mAG-hGeminin). Flow cytometric sorting of GFP(+) cells from doxorubicin-treated HFFs carrying mAG-hGeminin reporter enabled isolation and enrichment of live senescent cells in the culture. Our study develops a novel method to identify and isolate live premature senescent cells, thereby providing a new tool to study cellularsenescence. PMID:27503759

Cellularsenescence plays an important role in diverse biological processes such as tumorigenesis and organismal aging. However, lack of methods to specifically identify and isolate live senescent cells hampers the precise understanding of the molecular mechanisms regulating cellularsenescence. Here, we report that utilization of fluorescent ubiquitination-based cell cycle indicator (FUCCI) technology allows isolation of live premature senescent cells induced by doxorubicin treatment. Exposure of human foreskin fibroblasts (HFFs) to a low dose of doxorubicin led to cellularsenescent phenotypes including formation of γ-H2AX and 53BP1 foci indicative of DNA damage, decreased cell proliferation and increased senescence-associated β-galactosidase (SA-β-gal) activity. Importantly, doxorubicin-induced senescent cells were arrested at S/G2/M phases of cell cycle which can be reported by a construct encoding a fragment of hGeminin fused with monomeric Azami-Green (mAG-hGeminin). Flow cytometric sorting of GFP+ cells from doxorubicin-treated HFFs carrying mAG-hGeminin reporter enabled isolation and enrichment of live senescent cells in the culture. Our study develops a novel method to identify and isolate live premature senescent cells, thereby providing a new tool to study cellularsenescence. PMID:27503759

Leaf senescence is a complicated developmental process that involves degenerative changes and nutrient recycling. The progress of leaf senescence is controlled by various environmental cues and plant hormones, including ethylene, jasmonic acid, salicylic acid, abscisic acid, cytokinins, and strigolactones. The production of strigolactones is induced in response to nitrogen and phosphorous deficiency. Strigolactones also accelerate leaf senescence and regulate shoot branching and root architecture. Leaf senescence is actively promoted in a nutrient-poor soil environment, and nutrients are transported from old leaves to young tissues and seeds. Strigolactones might act as important signals in response to nutrient levels in the rhizosphere. In this review, we discuss the possible roles of strigolactones during leaf senescence. PMID:27135345

Dephasing representation of fidelity, also known as the phase averaging method, can be considered as a special case of Miller's linearized semiclassical initial value representation and belongs among the most efficient approximate semiclassical approaches for the calculation of ultrafast time-resolved electronic spectra. Recently it has been shown that the number of trajectories required for convergence of this method is independent of the system's dimensionality. Here we propose a further accelerated version of the dephasing representation in the spirit of Heller's cellular dynamics. The basic idea of the 'cellular dephasing representation' is to decompose the Wigner transform of the initial state into a phase space Gaussian basis and then evaluate the contribution of each Gaussian to the relevant correlation function approximately analytically, using numerically acquired information only along the trajectory of the Gaussian's centre. The approximate nature of the DR classifies it among semiclassical perturbation approximations proposed by Miller and Smith, and suggests its limited accuracy. Yet, the proposed method turns out to be sufficiently accurate whenever the interaction with the environment diminishes the importance of recurrences in the correlation functions of interest. Numerical tests on a collinear NCO molecule indicate that even results based on a single classical trajectory are in a remarkable agreement with the fully converged DR requiring approximately 104 trajectories.

The effects of acute Salmonella typhimurium sepsis on the kinetics of peripheral L-thyroxine (T4) distribution and metabolism and on serum total and free T4 concentrations were studied in rhesus monkeys inoculated i.v. with either heat-killed or viable organisms. The rate of disappearance of labeled T4 from serum was increased within 8 h after inoculation of monkeys with either heat-killed or viable Salmonella. The effects of the heat-killed organisms were transient and no longer evident by 16 h postinoculation. The monkeys inoculated with the viable Salmonella experienced a 2-3 day febrile, septic illness that was accompanied by an increase in the absolute rate of T4 disposal. In the infected monkeys, serum total T4 and endogenously labeled protein-bound iodine concentrations fell significantly during the period of acute sepsis and then rose during convalescence to values that exceeded the preinoculation values, suggesting that thyroidal secretion of hormone had increased in response to a primary depletion of the peripheral hormonal pool. Total cellular and hepatic uptakes of T4 were enhanced by 4 h after inoculation of monkeys with either heat-killed or viable Salmonella, but the increase in total cellular uptake persisted for 24 h only in the monkeys inoculated with the viable organisms. These alterations in T4 kinetics could neither be correlated with changes in the binding of T4 in plasma nor attributed to an increase in vascular permeability. Moreover, they could not be ascribed to an in vitro product of bacterial growth, suggesting that the presence of the organisms themselves was required. An acceleration of T4 disappearance was also observed during Escherichia coli and Diplococcus pucumoniae bacteremias. Our findings are consistent with a primary increase in the cellular uptake and metabolism of T4 during bacterial sepsis, possibly related to phagocytic cell function in the host. PMID:4629910

Accelerator mass spectrometry (AMS) is a highly sensitive analytical methodology used to quantify the content of radioisotopes, such as {sup 14}C, in a sample. The primary goals of this work were to demonstrate the utility of AMS in determining cellular [{sup 14}C]doxorubicin (DOX) concentrations and to develop a sensitive assay that is superior to high performance liquid chromatography (HPLC) for the quantification of DOX at the tumor level. In order to validate the superior sensitivity of AMS versus HPLC with fluorescence detection, we performed three studies comparing the cellular accumulation of DOX: one in vitro cell line study, and two in vivo xenograft mouse studies. Using AMS, we quantified cellular DOX content up to 4 hours following in vitro exposure at concentrations ranging from 0.2 pg/ml (345 fM) to 2 {micro}g/ml (3.45 {micro}M) [{sup 14}C]DOX. The results of this study show that, compared to standard fluorescence-based HPLC, the AMS method was over five orders of magnitude more sensitive. Two in vivo studies compared the sensitivity of AMS to HPLC using a nude mouse xenograft model in which breast cancer cells were implanted subcutaneously. After sufficiently large tumors formed, DOX was administered intravenously at two dose levels. Additionally, we tested the AMS method in a nude mouse xenograft model of multidrug resistance (MDR) in which each mouse was implanted with both wild type and MDR+ cells on opposite flanks. The results of the second and third studies showed that DOX concentrations were significantly higher in the wild type tumors compared to the MDR+ tumors, consistent with the MDR model. The extreme sensitivity of AMS should facilitate similar studies in humans to establish target site drug delivery and to potentially determine the optimal treatment dose and regimen.

Researcher Dr. Yi Li developed a technique to manipulate certain characteristics of plant growth such as anit-senescence. For example, the tobacco leaf was clipped from a transgenic plant (right), and a wildtype plant (left). During ground-based laboratory studies, both leaves were left in a darkened area for 4 months. When retrieved, the wildtype plant leaf was dried-out and the transgenic leaf remained fresh and green. A variation of this technology that involves manipulating plant hormones has been conducted in space-based studies on tomato plants through BioServe Space Technologies. The transport and distribution of auxin, an important plant hormone has shown to be influenced by microgravity, which could lead to improving the quality of fruits and vegetables grown on Earth.

Cellularsenescence is a tumor suppressor mechanism where cells enter a permanent growth arrest following cellular stress. Oncogene-induced senescence (OIS) is induced in non-malignant cells following the expression of an oncogene or inactivation of a tumor suppressor. Previously, we have shown that protein kinase C iota (PKCι) depletion induces cellularsenescence in glioblastoma cells in the absence of a detectable DNA damage response. Here we demonstrate that senescent glioblastoma cells exhibit an aberrant centrosome morphology. This was observed in basal levels of senescence, in p21-induced senescence, and in PKCι depletion-induced senescence. In addition, senescent glioblastoma cells are polyploid, Ki-67 negative and arrest at the G1/S checkpoint, as determined by expression of cell cycle regulatory proteins. These markers are all consistent with cells that have undergone mitotic slippage. Failure of the spindle assembly checkpoint to function properly can lead to mitotic slippage, resulting in the premature exit of mitotic cells into the G1 phase of the cell cycle. Although in G1, these cells have the replicated DNA and centrosomal phenotype of a cell that has entered mitosis and failed to divide. Overall, we demonstrate that PKCι depletion initiates mitotic slippage-induced senescence in glioblastoma cells. To our knowledge, this is the first evidence of markers of mitotic slippage directly in senescent cells by co-staining for senescence-associated β-galactosidase and immunofluorescence markers in the same cell population. We suggest that markers of mitotic slippage be assessed in future studies of senescence to determine the extent of mitotic slippage in the induction of cellularsenescence. PMID:26208522

Cellularsenescence is an anti-proliferative program that restricts the propagation of cells subjected to different kinds of stress. Cellularsenescence was initially described as a cell-autonomous tumor suppressor mechanism that triggers an irreversible cell cycle arrest that prevents the proliferation of damaged cells at risk of neoplastic transformation. However, discoveries during the last decade have established that senescent cells can also impact the surrounding tissue microenvironment and the neighboring cells in a non-cell-autonomous manner. These non-cell-autonomous activities are, in part, mediated by the selective secretion of extracellular matrix degrading enzymes, cytokines, chemokines and immune modulators, which collectively constitute the senescence-associated secretory phenotype. One of the key functions of the senescence-associated secretory phenotype is to attract immune cells, which in turn can orchestrate the elimination of senescent cells. Interestingly, the clearance of senescent cells seems to be critical to dictate the net effects of cellularsenescence. As a general rule, the successful elimination of senescent cells takes place in processes that are considered beneficial, such as tumor suppression, tissue remodeling and embryonic development, while the chronic accumulation of senescent cells leads to more detrimental consequences, namely, cancer and aging. Nevertheless, exceptions to this rule may exist. Now that cellularsenescence is in the spotlight for both anti-cancer and anti-aging therapies, understanding the precise underpinnings of senescent cell removal will be essential to exploit cellularsenescence to its full potential. PMID:27417123

Senescent cells accumulate during ageing in various tissues and contribute to organismal ageing. However, factors that are involved in the induction of senescence in vivo are still not well understood. SNEV(P) (rp19/) (PSO) (4) is a multifaceted protein, known to be involved in DNA damage repair and senescence, albeit only in vitro. In this study, we used heterozygous SNEV(+/-) mice (SNEV-knockout results in early embryonic lethality) and wild-type littermate controls as a model to elucidate the role of SNEV(P) (rp19/) (PSO) (4) in DNA damage repair and senescence in vivo. We performed PUVA treatment as model system for potently inducing cellularsenescence, consisting of 8-methoxypsoralen in combination with UVA on mouse skin to induce DNA damage and premature skin ageing. We show that SNEV(P) (rp19/) (PSO) (4) expression decreases during organismal ageing, while p16, a marker of ageing in vivo, increases. In response to PUVA treatment, we observed in the skin of both SNEV(P) (rp19/) (PSO) (4) and wild-type mice an increase in γ-H2AX levels, a DNA damage marker. In old SNEV(P) (rp19/) (PSO) (4) mice, this increase is accompanied by reduced epidermis thickening and increase in p16 and collagenase levels. Thus, the DNA damage response occurring in the mouse skin upon PUVA treatment is dependent on SNEV(P) (rp19/) (PSO) (4) expression and lower levels of SNEV(P) (rp19/) (PSO) (4) , as in old SNEV(+/-) mice, result in increase in cellularsenescence and acceleration of premature skin ageing. PMID:26663487

Eldecalcitol (ELD), a 2β-hydroxypropyloxy derivative of 1α,25(OH)2D3, is a potent inhibitor of bone resorption that has demonstrated a greater effect at reducing the risk of fracture in osteoporotic patients than alfacalcidol (ALF). In the present study, we used the senescence-accelerated mouse strain P6 (SAM/P6), which has low bone mass caused by osteoblast dysfunction, to evaluate the effect of ELD on cortical bone in comparison with ALF. Four-month-old SAM/P6 mice were given either ELD (0.025 or 0.05μg/kg) or ALF (0.2 or 0.4μg/kg) by oral gavage 5 times/week for 6 weeks. Both ELD and ALF increased serum calcium (Ca) in a dose-dependent manner. Serum Ca levels in the ELD 0.05μg/kg group were comparable to those of the ALF 0.2μg/kg group. ELD 0.05μg/kg significantly improved the bone biomechanical properties of the femur compared with the vehicle control group (p<0.001) and the ALF 0.2μg/kg group (p<0.05) evaluated by 3-point bending test. The cortical area of the mid-femur in the ELD 0.05μg/kg group but not the ALF 0.2μg/kg group was significantly higher than those of the vehicle control group (p<0.001). Bone histomorphometry revealed that in the femoral endocortical surface, the suppression of bone resorption parameters (N.Oc/BS) and bone formation parameters (MS/BS) by ELD (0.05μg/kg) was greater than that by ALF (0.2μg/kg). In contrast, in the femoral periosteal surface, ELD 0.05μg/kg significantly increased bone formation parameters (BFR/BS, MS/BS) compared with the vehicle control group (p<0.05, p<0.01, respectively), whereas ALF 0.2μg/kg did not alter these parameters. These results indicate that ELD improved the biomechanical properties of femoral cortical bone not only by inhibiting endocortical bone resorption but also by stimulating the periosteal bone formation in SAM/P6 mice. This article is part of a Special Issue entitled '16th Vitamin D Workshop'. PMID:24189542

The role of senescence as a tumor suppressor is well established; however, recent evidence has revealed novel paracrine functions for senescent cells in relation to their microenvironment, most notably protumorigenic roles in certain contexts. Senescent cells are capable of altering the inflammatory microenvironment through the senescence-associated secretory phenotype, which could have important consequences for tumorigenesis. The role of senescent cells in a highly inflammatory cancer like pancreatic cancer is still largely undefined, apart from the fact that senescence abrogation increases tumorigenesis in vivo. This review will summarize our current knowledge of the phenomenon of cellularsenescence in pancreatic ductal adenocarcinoma, its overlapping link with inflammation, and some urgent unanswered questions in the field. PMID:27451122

Mesenchymal stem cells (MSCs) contribute to tissue repair in vivo and form an attractive cell source for tissue engineering. Their regenerative potential is impaired by cellularsenescence. The effects of oxidative stress on MSCs are still unknown. Our studies were to investigate into the proliferation potential, cytological features and the telomere linked stress response system of MSCs, subject to acute or prolonged oxidant challenge with hydrogen peroxide. Telomere length was measured using the telomere restriction fragment assay, gene expression was determined by rtPCR. Sub-lethal doses of oxidative stress reduced proliferation rates and induced senescent-morphological features and senescence-associated {beta}-galactosidase positivity. Prolonged low dose treatment with hydrogen peroxide had no effects on cell proliferation or morphology. Sub-lethal and prolonged low doses of oxidative stress considerably accelerated telomere attrition. Following acute oxidant insult p21 was up-regulated prior to returning to initial levels. TRF1 was significantly reduced, TRF2 showed a slight up-regulation. SIRT1 and XRCC5 were up-regulated after oxidant insult and expression levels increased in aging cells. Compared to fibroblasts and chondrocytes, MSCs showed an increased tolerance to oxidative stress regarding proliferation, telomere biology and gene expression with an impaired stress tolerance in aged cells.

One of the leading causes of long-term kidney graft loss is chronic allograft injury (CAI), a pathological process triggered by alloantigen-dependent and alloantigen-independent factors. Alloantigen-independent factors, such as cold ischemia (CI) may amplify the recipient immune response against the graft. We investigated the impact of prolonged cold ischemia and the subsequent delayed graft function on CAI in a fully MHC-mismatched rat model of kidney allotransplantation. Prolonged CI was associated with anticipation of proteinuria onset and graft function deterioration (ischemia: 90d; no ischemia: 150d), more severe tubular atrophy, interstitial fibrosis, and glomerulosclerosis, and increased mortality rate (180d survival, ischemia: 0%; no ischemia: 67%). In ischemic allografts, T and B cells were detected very early and were organized in inflammatory clusters. Higher expression of BAFF-R and TACI within the ischemic allografts indicates that B cells are mature and activated. As a consequence of B cell activity, anti-donor antibodies, glomerular C4d and IgG deposition, important features of chronic humoral rejection, appeared earlier in ischemic than in non-ischemic allograft recipients. Thus, prolonged CI time plays a main role in CAI development by triggering acceleration of cellular and humoral reactions of chronic rejection. Limiting CI time should be considered as a main target in kidney transplantation. PMID:22239163

The incidence of pulmonary fibrosis increases with age. Studies from our group have implicated circulating progenitor cells, termed fibrocytes, in lung fibrosis. In this study, we investigate whether the preceding determinants of inflammation and fibrosis were augmented with aging. We compared responses to intratracheal bleomycin in senescence-accelerated prone mice (SAMP), with responses in age-matched control senescence-accelerated resistant mice (SAMR). SAMP mice demonstrated an exaggerated inflammatory response as evidenced by lung histology. Bleomycin-induced fibrosis was significantly higher in SAMP mice compared with SAMR controls. Consistent with fibrotic changes in the lung, SAMP mice expressed higher levels of transforming growth factor-beta1 in the lung. Furthermore, SAMP mice showed higher numbers of fibrocytes and higher levels of stromal cell-derived factor-1 in the peripheral blood. This study provides the novel observation that apart from increases in inflammatory and fibrotic factors in response to injury, the increased mobilization of fibrocytes may be involved in age-related susceptibility to lung fibrosis. PMID:19359440

Cellularsenescence is a stress response mechanism that limits tumorigenesis and tissue damage. Induction of cellularsenescence commonly coincides with an immunogenic phenotype that promotes self-elimination by components of the immune system, thereby facilitating tumor suppression and limiting excess fibrosis during wound repair. The mechanisms by which senescent cells regulate their immune surveillance are not completely understood. Here we show that ligands of an activating Natural Killer (NK) cell receptor (NKG2D), MICA and ULBP2 are consistently up-regulated following induction of replicative senescence, oncogene-induced senescence and DNA damage - induced senescence. MICA and ULBP2 proteins are necessary for efficient NK-mediated cytotoxicity towards senescent fibroblasts. The mechanisms regulating the initial expression of NKG2D ligands in senescent cells are dependent on a DNA damage response, whilst continuous expression of these ligands is regulated by the ERK signaling pathway. In liver fibrosis, the accumulation of senescent activated stellate cells is increased in mice lacking NKG2D receptor leading to increased fibrosis. Overall, our results provide new insights into the mechanisms regulating the expression of immune ligands in senescent cells and reveal the importance of NKG2D receptor-ligand interaction in protecting against liver fibrosis. PMID:26878797

Cellularsenescence is a stress response mechanism that limits tumorigenesis and tissue damage. Induction of cellularsenescence commonly coincides with an immunogenic phenotype that promotes self-elimination by components of the immune system, thereby facilitating tumor suppression and limiting excess fibrosis during wound repair. The mechanisms by which senescent cells regulate their immune surveillance are not completely understood. Here we show that ligands of an activating Natural Killer (NK) cell receptor (NKG2D), MICA and ULBP2 are consistently up-regulated following induction of replicative senescence, oncogene-induced senescence and DNA damage - induced senescence. MICA and ULBP2 proteins are necessary for efficient NK-mediated cytotoxicity towards senescent fibroblasts. The mechanisms regulating the initial expression of NKG2D ligands in senescent cells are dependent on a DNA damage response, whilst continuous expression of these ligands is regulated by the ERK signaling pathway. In liver fibrosis, the accumulation of senescent activated stellate cells is increased in mice lacking NKG2D receptor leading to increased fibrosis. Overall, our results provide new insights into the mechanisms regulating the expression of immune ligands in senescent cells and reveal the importance of NKG2D receptor-ligand interaction in protecting against liver fibrosis. PMID:26878797

Senescence is defined as a stable cell growth arrest. Oncogene-induced senescence (OIS) occurs in normal primary human cells after activation of an oncogene in the absence of other cooperating oncogenic stimuli. OIS is therefore considered a bona fide tumor suppression mechanism in vivo. Indeed, overcoming OIS-associated stable cell growth arrest can lead to tumorigenesis. Although cells that have undergone OIS do not replicate their DNA, they remain metabolically active. A number of recent studies report significant changes in cellular metabolism during OIS, including alterations in nucleotide, glucose, and mitochondrial metabolism and autophagy. These alterations may be necessary for stable senescence-associated cell growth arrest, and overcoming these shifts in metabolism may lead to tumorigenesis. This review highlights what is currently known about alterations in cellular metabolism during OIS and the implication of OIS-associated metabolic changes in cellular transformation and the development of cancer therapeutic strategies. PMID:27308349

Acute cellular stress caused by oncogene activation or high levels of DNA damage can engage a tumour suppressive response, which can lead to cellularsenescence. Chronic cellular stress evoked by low levels of DNA damage or telomere erosion is involved in the ageing process. In oncogene induced senescence in fibroblasts, a dramatic rearrangement of heterochromatin into foci and accumulation of constitutive heterochromatin is well documented. In contrast, a loss of heterochromatin has been described in replicative senescence and premature ageing syndromes. The distinct nuclear phenotypes that accompany the stress response highlight the differences between acute and chronic stress models, and this review will address the differences and similarities between these models with a focus on chromosome organisation and heterochromatin. PMID:27101466

Considering the early phylogenetic appearance of functional xylem and phloem elements and the range of senescent processes expressed onto genetically, it becomes apparent that such processes are inextricably linked to the evolution, development, reproduction, form, and function of higher plants. The importance of these senescent processes to man are patently obvious since, in one form or another, these processes provide major sources of wood, fiber, and fuel, and are involved in seed development and grain and fruit ripening. To many, the results of senescent processes also have esthetic value including, for example, the grandeur of a Sequoia, the blaze of colors across a desert landscape covered in the spring by ephermal flowers, or the rich tones and panoramic splendor of a deciduous forest in autumn. Senescent processes are widespread, but varied in kind and degree, ranging from whole plants to individual tissues and cells. This symposium was organized primarily around cellular and biochemical aspects of senescence. A major emphasis was the view that senescent processes, and those which developmentally lead to senescence, are highly regulated with an underlying genetic component. Individual papers were processed separately for the database.

Recombinant polynucleotides have expression control sequences that have a senescence responsive element and a minimal promoter, and which are operatively linked to a heterologous nucleotide sequence. The molecules are useful for achieving high levels of expression of genes in senescent cells. Methods of inhibiting expression of genes in senescent cells also are provided.

Recombinant polynucleotides have expression control sequences that have a senescence responsive element and a minimal promoter, and which are operatively linked to a heterologous nucleotide sequence. The molecules are useful for achieving high levels of expression of genes in senescent cells. Methods of inhibiting expression of genes in senescent cells also are provided.

Oilseed rape (Brassica napus L.) is a crop plant characterized by a poor nitrogen (N) use efficiency that is mainly due to low N remobilization efficiency during the sequential leaf senescence of the vegetative stage. As a high leaf N remobilization efficiency was strongly linked to a high remobilization of proteins during leaf senescence of rapeseed, our objective was to identify senescence-associated protease activities implicated in the protein degradation. To reach this goal, leaf senescence processes and protease activities were investigated in a mature leaf becoming senescent in plants subjected to ample or low nitrate supply. The characterization of protease activities was performed by using in vitro analysis of RuBisCO degradation with or without inhibitors of specific protease classes followed by a protease activity profiling using activity-dependent probes. As expected, the mature leaf became senescent regardless of the nitrate treatment, and nitrate limitation enhanced the senescence processes associated with an enhanced degradation of soluble proteins. The characterization of protease activities revealed that: (i) aspartic proteases and the proteasome were active during senescence regardless of nitrate supply, and (ii) the activities of serine proteases and particularly cysteine proteases (Papain-like Cys proteases and vacuolar processing enzymes) increased when protein remobilization associated with senescence was accelerated by nitrate limitation. Short statement: Serine and particularly cysteine proteases (both PLCPs and VPEs) seem to play a crucial role in the efficient protein remobilization when leaf senescence of oilseed rape was accelerated by nitrate limitation. PMID:26993244

The molecular mechanisms that contribute to the initiation and progression of head and neck squamous cell carcinoma (HNSCC) have not been completely delineated. Our observations indicate that defects in the transforming growth factor-β and PI3K/Akt signaling pathways are common in human HNSCCs. Conditional activation of the PI3K/Akt pathway due to Pten deletion in the mouse head and neck epithelia gives rise to hyperproliferation, but only a few lesions progress to HNSCC. However, Pten-deficient mice developed full-penetrance HNSCC in combination with type I TGF-β receptor (Tgfbr1) deletion. Molecular analysis revealed enhanced cell proliferation, decreased apoptosis, and increased expression of CCND1 in the basal layer of the head and neck epithelia, as well as in the tumors of Tgfbr1/Pten double conditional knockout (2cKO) mice. Furthermore, neoplastic transformation involves senescence evasion, and is associated with an increased number of putative cancer stem cells. In addition, the nuclear factor-κB pathway activation, myeloid-derived suppressor cell infiltration, angiogenesis and immune suppression in the tumor microenvironment, all of which are characteristics of human HNSCCs, contribute significantly to head and neck carcinogenesis in 2cKO mice. These tumors display pathology and multiple molecular alterations resembling human HNSCCs. This suggests that the Tgfbr1/Pten 2cKO mouse model is suitable for preclinical intervention, and that it has significant implications in the development of diagnostic cancer biomarkers and effective strategies for prevention and treatment of HNSCCs. PMID:22037217

Ovariectomy (OVX)-induced bone loss has been linked to increased bone turnover and higher bone matrix collagen degradation as the result of osteoclast activation. However, the role of degraded collagen matrix in the fate of resident bone-forming cells is unclear. In this report, we show that OVX-induced bone loss is associated with profound decreases in collagen 1 and Sirt1. This was accompanied by increases in expression and activity of the senescence marker collagenase and expression of p16/p21 in bone. Feeding a diet supplemented with blueberries (BB) to pre-pubertal rats throughout development or only prior to puberty [postnatal day 21 (PND21) to PND34] prevents OVX-induced effects on expression of these molecules at PND68. In order to provide more evidence and gain a better understanding on the association between bone collagen matrix and resident bone cell fate, in vitro studies on the cellularsenescence pathway using primary calvarial cells and three cell lines (ST2 cells, OB6, and MLO-Y4) were conducted. We found that senescence was inhibited by collagen in a dose-response manner. Treatment of cells with serum from OVX rats accelerated osteoblastic cell senescence pathways, but serum from BB-fed OVX rats had no effect. In the presence of low collagen or treatment with OVX rat serum, ST2 cells exhibited higher potential to differentiate into adipocytes. Finally, we demonstrated that bone cell senescence is associated with decreased Sirt1 expression and activated p53, p16, and p21. These results suggest that (1) a significant prevention of OVX-induced bone cell senescence from adult rats can occur after only 14 days consumption of a BB-containing diet immediately prior to puberty, and (2) the molecular mechanisms underlying this effect involves, at least in part, prevention of collagen degradation. PMID:22555620

Background Chronic Hepatitis B virus (HBV) infection can lead to the development of chronic hepatitis, cirrhosis and hepatocellular carcinoma. We hypothesized that HBV might accelerate hepatocyte ageing and investigated the effect of HBV on hepatocyte cell cycle state and biological age. We also investigated the relation between inflammation, fibrosis and cell cycle phase. Methods Liver samples from patients with chronic HBV (n = 91), normal liver (n = 55) and regenerating liver (n = 15) were studied. Immunohistochemistry for cell cycle phase markers and HBV antigens was used to determine host cell cycle phase. Hepatocyte-specific telomere length was evaluated by quantitative fluorescent in-situ hybridization (Q-FISH) in conjunction with hepatocyte nuclear area and HBV antigen expression. The effects of induced cell cycle arrest and induced cellularsenescence on HBV production were assessed in vitro. Results 13.7% hepatocytes in chronic HBV had entered cell cycle, but expression of markers for S, G2 and M phase was low compared with regenerating liver. Hepatocyte p21 expression was increased (10.9%) in chronic HBV and correlated with liver fibrosis. Mean telomere length was reduced in chronic HBV compared to normal. However, within HBV-affected livers, hepatocytes expressing HBV antigens had longer telomeres. Telomere length declined and hepatocyte nuclear size increased as HBV core antigen (HBcAg) expression shifted from the nucleus to cytoplasm. Nuclear co-expression of HBcAg and p21 was not observed. Cell cycle arrest induced in vitro was associated with increased HBV production, in contrast to in vitro induction of cellularsenescence, which had no effect. Conclusion Chronic HBV infection was associated with hepatocyte G1 cell cycle arrest and accelerated hepatocyte ageing, implying that HBV induced cellularsenescence. However, HBV replication was confined to biologically younger hepatocytes. Changes in the cellular location of HBcAg may be related to the

ABSTRACT The accumulation of senescent disc cells in degenerative intervertebral disc (IVD) suggests the detrimental roles of cell senescence in the pathogenesis of intervertebral disc degeneration (IDD). Disc cell senescence decreased the number of functional cells in IVD. Moreover, the senescent disc cells were supposed to accelerate the process of IDD via their aberrant paracrine effects by which senescent cells cause the senescence of neighboring cells and enhance the matrix catabolism and inflammation in IVD. Thus, anti-senescence has been proposed as a novel therapeutic target for IDD. However, the development of anti-senescence therapy is based on our understanding of the molecular mechanism of disc cell senescence. In this review, we focused on the molecular mechanism of disc cell senescence, including the causes and various molecular pathways. We found that, during the process of IDD, age-related damages together with degenerative external stimuli activated both p53-p21-Rb and p16-Rb pathways to induce disc cell senescence. Meanwhile, disc cell senescence was regulated by multiple signaling pathways, suggesting the complex regulating network of disc cell senescence. To understand the mechanism of disc cell senescence better contributes to developing the anti-senescence-based therapies for IDD. PMID:27192096

Approaches the regulation of aging by perturbing the rate of senescent changes in studying how the modulating agent exerts its effects. Shows that very subtle molecular changes may be involved in the overall regulation of cellular aging. (Author/BL)

Degreening, caused by chlorophyll degradation, is the most obvious symptom of senescing leaves. Chlorophyll degradation can be triggered by endogenous and environmental cues, and ethylene is one of the major inducers. ETHYLENE INSENSITIVE3 (EIN3) is a key transcription factor in the ethylene signaling pathway. It was previously reported that EIN3, miR164, and a NAC (NAM, ATAF, and CUC) transcription factor ORE1/NAC2 constitute a regulatory network mediating leaf senescence. However, how this network regulates chlorophyll degradation at molecular level is not yet elucidated. Here we report a feed-forward regulation of chlorophyll degradation that involves EIN3, ORE1, and chlorophyll catabolic genes (CCGs). Gene expression analysis showed that the induction of three major CCGs, NYE1, NYC1 and PAO, by ethylene was largely repressed in ein3 eil1 double mutant. Dual-luciferase assay revealed that EIN3 significantly enhanced the promoter activity of NYE1, NYC1 and PAO in Arabidopsis protoplasts. Furthermore, Electrophoretic mobility shift assay (EMSA) indicated that EIN3 could directly bind to NYE1, NYC1 and PAO promoters. These results reveal that EIN3 functions as a positive regulator of CCG expression during ethylene-mediated chlorophyll degradation. Interestingly, ORE1, a senescence regulator which is a downstream target of EIN3, could also activate the expression of NYE1, NYC1 and PAO by directly binding to their promoters in EMSA and chromatin immunoprecipitation (ChIP) assays. In addition, EIN3 and ORE1 promoted NYE1 and NYC1 transcriptions in an additive manner. These results suggest that ORE1 is also involved in the direct regulation of CCG transcription. Moreover, ORE1 activated the expression of ACS2, a major ethylene biosynthesis gene, and subsequently promoted ethylene production. Collectively, our work reveals that EIN3, ORE1 and CCGs constitute a coherent feed-forward loop involving in the robust regulation of ethylene-mediated chlorophyll degradation

Multiple mechanisms of senescence induction exist including telomere attrition, oxidative stress, oncogene expression and DNA damage signalling. The regulation of the cellular changes required to respond to these stimuli and create the complex senescent cell phenotype has many different mechanisms. MiRNAs present one mechanism by which genes with diverse functions on multiple pathways can be simultaneously regulated. In this study we investigated 12 miRNAs previously identified as senescence regulators. Using pathway analysis of their target genes we tested the relevance of miRNA regulation in the induction of senescence. Our analysis highlighted the potential of these senescence-associated miRNAs (SA-miRNAs) to regulate the cell cycle, cytoskeletal remodelling and proliferation signalling logically required to create a senescent cell. The reanalysis of publicly available gene expression data from studies exploring different senescence stimuli also revealed their potential to regulate core senescence processes, regardless of stimuli. We also identified stimulus specific apoptosis survival pathways theoretically regulated by the SA-miRNAs. Furthermore the observation that miR-499 and miR-34c had the potential to regulate all 4 of the senescence induction types we studied highlights their future potential as novel drug targets for senescence induction. PMID:19419692

The TERT gene encodes for the reverse transcriptase activity of the telomerase complex and mutations in TERT can lead to dysfunctional telomerase activity resulting in diseases such as dyskeratosis congenita (DKC). Here, we describe a novel TERT mutation at position T1129P leading to DKC with progressive bone marrow (BM) failure in homozygous members of a consanguineous family. BM hematopoietic stem cells (HSCs) of an affected family member were 300-fold reduced associated with a significantly impaired colony forming capacity in vitro and impaired repopulation activity in mouse xenografts. Recent data in yeast suggested improved cellular checkpoint controls by mTOR inhibition preventing cells with short telomeres or DNA damage from dividing. To evaluate a potential therapeutic option for the patient, we treated her primary skin fibroblasts and BM HSCs with the mTOR inhibitor rapamycin. This led to prolonged survival and decreased levels of senescence in T1129P mutant fibroblasts. In contrast, the impaired HSC function could not be improved by mTOR inhibition, as colony forming capacity and multilineage engraftment potential in xenotransplanted mice remained severely impaired. Thus, rapamycin treatment did not rescue the compromised stem cell function of TERTT1129P mutant patient HSCs and outlines limitations of a potential DKC therapy based on rapamycin. PMID:26546739

The TERT gene encodes for the reverse transcriptase activity of the telomerase complex and mutations in TERT can lead to dysfunctional telomerase activity resulting in diseases such as dyskeratosis congenita (DKC). Here, we describe a novel TERT mutation at position T1129P leading to DKC with progressive bone marrow (BM) failure in homozygous members of a consanguineous family. BM hematopoietic stem cells (HSCs) of an affected family member were 300-fold reduced associated with a significantly impaired colony forming capacity in vitro and impaired repopulation activity in mouse xenografts. Recent data in yeast suggested improved cellular checkpoint controls by mTOR inhibition preventing cells with short telomeres or DNA damage from dividing. To evaluate a potential therapeutic option for the patient, we treated her primary skin fibroblasts and BM HSCs with the mTOR inhibitor rapamycin. This led to prolonged survival and decreased levels of senescence in T1129P mutant fibroblasts. In contrast, the impaired HSC function could not be improved by mTOR inhibition, as colony forming capacity and multilineage engraftment potential in xenotransplanted mice remained severely impaired. Thus, rapamycin treatment did not rescue the compromised stem cell function of TERTT1129P mutant patient HSCs and outlines limitations of a potential DKC therapy based on rapamycin. PMID:26546739

Senescence is characterized by permanent cell-cycle arrest despite continued viability and metabolic activity, in conjunction with the secretion of a complex mixture of extracellular proteins and soluble factors known as the senescence-associated secretory phenotype (SASP). Cellularsenescence has been shown to prevent the proliferation of potentially tumorigenic cells, and is thus generally considered a tumor suppressive process. However, some SASP components may act as pro-tumorigenic mediators on premalignant cells in the microenvironment. A limited number of studies indicated that protein kinase C (PKC) has a role in senescence, with different isoforms having opposing effects. It is therefore important to elucidate the functional role of specific PKCs in senescence. Here we show that PKCη, an epithelial specific and anti-apoptotic kinase, promotes senescence induced by oxidative stress and DNA damage. We further demonstrate that PKCη promotes senescence through its ability to upregulate the expression of the cell cycle inhibitors p21Cip1 and p27Kip1 and enhance transcription and secretion of interleukin-6 (IL-6). Moreover, we demonstrate that PKCη creates a positive loop for reinforcing senescence by increasing the transcription of both IL-6 and IL-6 receptor, whereas the expression of IL-8 is specifically suppressed by PKCη. Thus, the presence/absence of PKCη modulates major components of SASP. Furthermore, we show that the human polymorphic variant of PKCη, 374I, that exhibits higher kinase activity in comparison to WT-374V, is also more effective in IL-6 secretion, p21Cip1 expression and the promotion of senescence, further supporting a role for PKCη in senescence. As there is now considerable interest in senescence activation/elimination to control tumor progression, it is first crucial to reveal the molecular regulators of senescence. This will improve our ability to develop new strategies to harness senescence as a potential cancer therapy in the

As aged population dramatically increases in these decades, efforts should be made on the intervention for curing age-associated neurologic degenerative diseases such as Alzheimer's disease (AD). Caffeoylquinic acid (CQA), an antioxidant component and its derivatives are natural functional compounds isolated from a variety of plants. In this study, we determined the neuroprotective effect of 3,5-di-O-CQA on Abeta(1-42) treated SH-SY5Y cells using MTT assay. To investigate the possible neuroprotective mechanism of 3,5-di-O-CQA, we performed proteomics analysis, real-time PCR analysis and measurement of the intracellular ATP level. In addition, we carried out the measurement of escape latency time to find the hidden platform in Morris water maze (MWM), real-time PCR using senescence-accelerated-prone mice (SAMP) 8 and senescence-accelerated-resistant mice (SAMR) 1 mice. Results showed that 3,5-di-O-CQA had neuroprotective effect on Abeta (1-42) treated cells. The mRNA expression of glycolytic enzyme (phosphoglycerate kinase-1; PGK1) and intracellular ATP level were increased in 3,5-di-O-CQA treated SH-SY5Y cells. We also found that 3,5-di-O-CQA administration induced the improvement of spatial learning and memory on SAMP8 mice, and the overexpression of PGK1 mRNA. These findings suggest that 3,5-di-O-CQA has a neuroprotective effect on neuron through the upregulation of PGK1 expression and ATP production activation. PMID:20570715

Cellularsenescence of endothelial cells plays an important role in the development of vascular lesions that ultimately lead to an atherosclerotic plaque. This review focuses on the age-related changes of endothelial and vascular smooth muscle cells that contribute to vascular disease and discusses potential new targets that could rejuvenate the vascular system and thereby prevent or delay atherosclerosis. PMID:26634025

August Weismann popularized the notion that metazoans have a potentially immortal germ line separated from a mortal soma, and evolutionary biologists regard senescence as an evolved characteristic of the soma. Many have claimed that metazoans that do not sequester their germ line have no clear distinction between germ line and soma, and consequently they should lack senescence. Here we present experimental evidence that senescence occurs in the asexually reproducing marine oligochaete Paranais litoralis. We also analyze data reported in Sonneborn's classical study and show that the rhabdocoel Stenostomum incaudatum undergoes senescence. We argue that the stability of commitment to somatic function and the fact that asexual metazoans form their germ cells from undifferentiated stem cells are sufficient to allow for senescence of the asexual metazoan's soma. Thus the evolution of somatic differentiation, and not germ-line sequestration, would be the necessary condition for the evolution of senescence. PMID:11607334

Cellularsenescence is historically associated with cancer suppression and aging. Recently, the reach of the senescence genetic program has been extended to include the ability of senescent cells to actively participate in tissue remodelling during many physiological processes, including placental biology, embryonic patterning, wound healing, and tissue stress responses caused by cancer therapy. Besides growth arrest, a significant feature of senescent cells is their ability to modify their immediate microenvironment using a senescence-associated (SA) secretome, commonly termed the SA secretory phenotype (SASP). Among others, the SASP contains growth factors, cytokines, and extracellular proteases that modulate the majority of both the beneficial and detrimental microenvironmental phenotypes caused by senescent cells. The SASP is thus becoming an obvious pharmaceutical target to manipulate SA effects. Herein, we review known signalling pathways underlying the SASP, including the DNA damage response (DDR), stress kinases, inflammasome, alarmin, inflammation- and cell survival-related transcription factors, miRNAs, RNA stability, autophagy, chromatin components, and metabolic regulators. We also describe the SASP as a temporally regulated dynamic sub-program of senescence that can be divided into a rapid DDR-associated phase, an early self-amplification phase, and a late "mature" phase, the late phase currently being the most widely studied SASP signature. Finally, we discuss how deciphering the signalling pathways regulating the SASP reveal targets that can be manipulated to harness the SA effects to benefit therapies for cancer and other age-related pathologies. PMID:27235851

Cellularsenescence is a process leading to terminal growth arrest with characteristic morphological features. This process is mediated by telomere-dependent, oncogene-induced and ROS-induced pathways, but persistent DNA damage is the most common cause. Senescence arrest is mediated by p16(INK4a)- and p21(Cip1)-dependent pathways both leading to retinoblastoma protein (pRb) activation. p53 plays a relay role between DNA damage sensing and p21(Cip1) activation. pRb arrests the cell cycle by recruiting proliferation genes to facultative heterochromatin for permanent silencing. Replicative senescence that occurs in hepatocytes in culture and in liver cirrhosis is associated with lack of telomerase activity and results in telomere shortening. Hepatocellular carcinoma (HCC) cells display inactivating mutations of p53 and epigenetic silencing of p16(INK4a). Moreover, they re-express telomerase reverse transcriptase required for telomere maintenance. Thus, senescence bypass and cellular immortality is likely to contribute significantly to HCC development. Oncogene-induced senescence in premalignant lesions and reversible immortality of cancer cells including HCC offer new potentials for tumor prevention and treatment. PMID:19070423

Tangier disease (TD) is characterized by a deficiency of high density lipoprotein (HDL) in plasma and patients with TD have an increased risk for coronary artery disease (CAD). Recently, we reported that fibroblasts from TD exhibited large and flattened morphology, which is often observed in senescent cells. On the other hand, data have accumulated to show the relationship between cellularsenescence and development of atherosclerotic CAD. The aim of the present study was to investigate whether TD fibroblasts exhibited cellularsenescence. The proliferation of TD fibroblasts was gradually decreased at population doubling level (PDL) {approx}10 compared with control cells. TD cells practically ceased proliferation at PDL {approx}30. DNA synthesis was markedly decreased in TD fibroblasts. TD cells exhibited a higher positive rate for senescence-associated {beta}-galactosidase (SA-{beta}-gal), which is one of the biomarkers of cellularsenescence in vitro. These data showed that TD cells reached cellularsenescence at an earlier PDL compared with controls. Although, there was no difference in the telomere length of fibroblasts between TD and controls at the earlier passage (PDL 6), the telomere length of TD cells was shorter than that of controls at the late passage (PDL 25). Taken together, the current study demonstrates that the late-passaged TD fibroblasts showed senescent phenotype in vitro, which might be related to the increased cardiovascular manifestations in TD patients.

Summary Cellularsenescence has been implicated in tumor suppression, development, and aging and is accompanied by large-scale chromatin rearrangements, forming senescence-associated heterochromatic foci (SAHF). However, how the chromatin is reorganized during SAHF formation is poorly understood. Furthermore, heterochromatin formation in senescence appears to contrast with loss of heterochromatin in Hutchinson-Gilford progeria. We mapped architectural changes in genome organization in cellularsenescence using Hi-C. Unexpectedly, we find a dramatic sequence- and lamin-dependent loss of local interactions in heterochromatin. This change in local connectivity resolves the paradox of opposing chromatin changes in senescence and progeria. In addition, we observe a senescence-specific spatial clustering of heterochromatic regions, suggesting a unique second step required for SAHF formation. Comparison of embryonic stem cells (ESCs), somatic cells, and senescent cells shows a unidirectional loss in local chromatin connectivity, suggesting that senescence is an endpoint of the continuous nuclear remodelling process during differentiation. PMID:25640177

In response to a variety of stresses, mammalian cells undergo a persistent proliferative arrest known as cellularsenescence. Many senescence-inducing stressors are potentially oncogenic, strengthening the notion that senescence evolved alongside apoptosis to suppress tumorigenesis. In contrast to apoptosis, senescent cells are stably viable and have the potential to influence neighboring cells through secreted soluble factors, which are collectively known as the senescence-associated secretory phenotype (SASP). However, the SASP has been associated with structural and functional tissue and organ deterioration and may even have tumor-promoting effects, raising the interesting evolutionary question of why apoptosis failed to outcompete senescence as a superior cell fate option. Here, we discuss the advantages that the senescence program may have over apoptosis as a tumor protective mechanism, as well as non-neoplastic functions that may have contributed to its evolution. We also review emerging evidence for the idea that senescent cells are present transiently early in life and are largely beneficial for development, regeneration and homeostasis, and only in advanced age do senescent cells accumulate to an organism’s detriment. PMID:25312810

Cellularsenescence suppresses cancer by preventing the proliferation of damaged cells, but senescent cells can also promote cancer though the pro-inflammatory senescence-associated secretory phenotype (SASP). Simvastatin, an HMG-coA reductase inhibitor, is known to attenuate inflammation and prevent certain cancers. Here, we show that simvastatin decreases the SASP of senescent human fibroblasts by inhibiting protein prenylation, without affecting the senescent growth arrest. The Rho family GTPases Rac1 and Cdc42 were activated in senescent cells, and simvastatin reduced both activities. Further, geranylgeranyl transferase, Rac1 or Cdc42 depletion reduced IL-6 secretion by senescent cells. We also show that simvastatin mitigates the effects of senescent conditioned media on breast cancer cell proliferation and endocrine resistance. Our findings identify a novel activity of simvastatin and mechanism of SASP regulation. They also suggest that senescent cells, which accumulate after radio/chemo therapy, promote endocrine resistance in breast cancer and that simvastatin might suppress this resistance. PMID:26658759

The progression of physiological ageing is driven by intracellular aberrations including telomere attrition, genomic instability, epigenetic alterations and loss of proteostasis. These in turn damage cells and compromise their functionality. Cellularsenescence, a stable irreversible cell-cycle arrest, is elicited in damaged cells and prevents their propagation in the organism. Under normal conditions, senescent cells recruit the immune system which facilitates their removal from tissues. Nevertheless, during ageing, tissue-residing senescent cells tend to accumulate, and might negatively impact their microenvironment via profound secretory phenotype with pro-inflammatory characteristics, termed senescence-associated secretory phenotype (SASP). Indeed, senescent cells are mostly abundant at sites of age-related pathologies, including degenerative disorders and malignancies. Interestingly, studies on progeroid mice indicate that selective elimination of senescent cells can delay age-related deterioration. This suggests that chronic inflammation induced by senescent cells might be a main driver of these pathologies. Importantly, senescent cells accumulate as a result of deficient immune surveillance, and their removal is increased upon the use of immune stimulatory agents. Insights into mechanisms of senescence surveillance could be combined with current approaches for cancer immunotherapy to propose new preventive and therapeutic strategies for age-related diseases. PMID:25217383

p53, a guardian of the genome, exerts its tumor suppression activity by regulating a large number of downstream targets involved in cell cycle arrest, DNA repair, apoptosis, and cellularsenescence. Although p53-mediated apoptosis is able to kill cancer cells, a role for cellularsenescence in p53-dependent tumor suppression is becoming clear. Mouse studies showed that activation of p53-induced premature senescence promotes tumor regression in vivo. However, p53-mediated cellularsenescence also leads to aging-related phenotypes, such as tissue atrophy, stem cell depletion, and impaired wound healing. In addition, several p53 isoforms and two p53 homologs, p63 and p73, have been shown to play a role in cellularsenescence and/or aging. Importantly, p53, p63, and p73 are necessary for the maintenance of adult stem cells. Therefore, understanding the dual role the p53 protein family in cancer and aging is critical to solve cancer and longevity in the future. In this chapter, we provide an overview on how p53, p63, p73, and their isoforms regulate cellularsenescence and aging. PMID:23296650

Cellularsenescence suppresses cancer by arresting cells at risk for malignant tumorigenesis. However, senescent cells also secrete molecules that can stimulate premalignant cells to proliferate and form tumors, suggesting the senescence response is antagonistically pleiotropic. We show that premalignant mammary epithelial cells exposed to senescent human fibroblasts in mice irreversibly lose differentiated properties, become invasive and undergo full malignant transformation. Moreover, using cultured mouse or human fibroblasts and non-malignant breast epithelial cells, we show that senescent fibroblasts disrupt epithelial alveolar morphogenesis, functional differentiation, and branching morphogenesis. Further, we identify MMP-3 as the major factor responsible for the effects of senescent fibroblasts on branching morphogenesis. Our findings support the idea that senescent cells contribute to age-related pathology, including cancer, and describe a new property of senescent fibroblasts--the ability to alter epithelial differentiation--that might also explain the loss of tissue function and organization that is a hallmark of aging.

Summary Cellularsenescence suppresses cancer by arresting cells at risk of malignant tumorigenesis. However, senescent cells also secrete molecules that can stimulate premalignant cells to proliferate and form tumors, suggesting the senescence response is antagonistically pleiotropic. We show that premalignant mammary epithelial cells exposed to senescent human fibroblasts in mice irreversibly lose differentiated properties, become invasive and undergo full malignant transformation. Moreover, using cultured mouse or human fibroblasts and non-malignant breast epithelial cells, we show that senescent fibroblasts disrupt epithelial alveolar morphogenesis, functional differentiation and branching morphogenesis. Furthermore, we identify MMP-3 as the major factor responsible for the effects of senescent fibroblasts on branching morphogenesis. Our findings support the idea that senescent cells contribute to age-related pathology, including cancer, and describe a new property of senescent fibroblasts – the ability to alter epithelial differentiation – that might also explain the loss of tissue function and organization that is a hallmark of aging. PMID:15657080

The present invention provides a biomarker system for the in vivo and in vitro assessment of cell senescence. In the method of the present invention, {beta}-galactosidase activity is utilized as a means by which cell senescence may be assessed either in vitro cell cultures or in vivo. 1 fig.

The present invention provides a biomarker system for the in vivo and in vitro assessment of cell senescence. In the method of the present invention, {beta}-galactosidase activity is utilized as a means by which cell senescence may be assessed either in in vitro cell cultures or in vivo. 1 fig.

Senescence represents the final stage of leaf development but is often induced prematurely following exposure to biotic and abiotic stresses. Leaf senescence is manifested by color change from green to yellow (due to chlorophyll degradation) or to red (due to de novo synthesis of anthocyanins coupled with chlorophyll degradation) and frequently culminates in programmed death of leaves. However, the breakdown of chlorophyll and macromolecules such as proteins and RNAs that occurs during leaf senescence does not necessarily represent a one-way road to death but rather a reversible process whereby senescing leaves can, under certain conditions, re-green and regain their photosynthetic capacity. This phenomenon essentially distinguishes senescence from programmed cell death, leading researchers to hypothesize that changes occurring during senescence might represent a process of trans-differentiation, that is the conversion of one cell type to another. In this review, we highlight attributes common to senescence and dedifferentiation including chromatin structure and activation of transposable elements and provide further support to the notion that senescence is not merely a deterioration process leading to death but rather a unique developmental state resembling dedifferentiation. PMID:27135333

The present invention provides a biomarker system for the in vivo and in vitro assessment of cell senescence. In the method of the present invention, .beta.-galactosidase activity is utilized as a means by which cell senescence may be assessed either in in vitro cell cultures or in vivo.

The present invention provides a biomarker system for the in vivo and in vitro assessment of cell senescence. In the method of the present invention, .beta.-galactosidase activity is utilized as a means by which cell senescence may be assessed either in vitro cell cultures or in vivo.

Cellularsenescence has emerged as a critical tumor suppressive mechanism in recent years, but relatively little is known about how senescence occurs. Here, we report that secreted Frizzled-related protein 1 (SFRP1), a secreted antagonist of Wnt signaling, is oversecreted upon cellularsenescence caused by DNA damage or oxidative stress. SFRP1 is necessary for stress-induced senescence caused by these factors and is sufficient for the induction of senescence phenotypes. We present evidence suggesting that SFRP1 functions as a secreted mediator of senescence through inhibition of Wnt signaling and activation of the retinoblastoma (Rb) pathway and that cancer-associated SFRP1 mutants are defective for senescence induction. PMID:22927647

Abstract Classic mechanisms of tumor response to chemotherapy include apoptosis and mitotic catastrophe. Recent studies have suggested that cellularsenescence, a terminal proliferationarrest seen in vitro, may be invoked during the exposure of cancer cells to chemotherapeutic agents. To identify markers associated specifically with the cellularsenescence phenotype, we utilized expression data from cDNA microarray experiments identifying transcripts whose expression levels increased as human prostate epithelial cells progressed to senescence. When screened against other growth-inhibitory conditions, including quiescence and apoptosis, many of these transcripts were also upregulated, indicating that similar pathways occur between apoptosis and senescence. A senescent-like phenotype was then induced in several prostate cancer cell lines using 5-aza-2′-deoxycytidine, doxorubicin, or Docetaxel. Treatment with these agents resulted in a significant increase in the induction of senescence-specific genes when compared to nonsenescent conditions. The performance of the panel was improved with fluorescence-activated cell sorting using PKH26 to isolate nonproliferating, viable, drug-treated populations, indicating that a heterogeneous response occurs with chemotherapy. We have defined an RNA-based gene panel that characterizes the senescent phenotype induced in cancer cells by drug treatment. These data also indicate that a panel of genes, rather than one marker, needs to be utilized to identify senescence. PMID:16229804

Evidence supporting the hypothesis that ethylene is involved in the control of senescence and abscission is reviewed. The data indicate that ethylene causes abscission in vivo by inhibiting auxin synthesis and transport or enhancing auxin destruction, thus lowering the diffusible auxin level. Studies with isolated leaves and explants suggest that the gas also may influence abscission by acceleratingsenescence and through an action on plant cell walls. Freshly prepared explants produce ethylene at a rate which must be high enough to maximally affect the tissue and this may explain why these explants (stage I) cannot respond to applied ethylene. PMID:16657016

The phosphate transporter PHT4;6 locates to the trans-Golgi compartment, and its impaired activity causes altered intracellular phosphate compartmentation, leading to low cytosolic Pi levels, a blockage of Golgi-related processes such as protein glycosylation and hemicellulose biosynthesis, and a dwarf phenotype. However, it was unclear whether altered Pi homeostasis in pht4;6 mutants causes further cellular problems, typically associated with limited phosphate availability. Here we report that pht4;6 mutants exhibit a markedly increased disposition to induce dark-induced senescence. In control experiments, in which pht4;6 mutants and wild-type plants developed similarly, we confirmed that accelerated dark-induced senescence in mutants is not a ‘pleiotropic’ process associated with the dwarf phenotype. In fact, accelerated dark-induced senescence in pht4;6 mutants correlates strongly with increased levels of toxic NH4 + and higher sensitivity to ammonium, which probably contribute to the inability of pht4;6 mutants to recover from dark treatment. Experiments with modified levels of either salicylic acid (SA) or trans-zeatin (tZ) demonstrate that altered concentrations of these compounds in pht4;6 plants act as major cellular mediators for dark-induced senescence. This conclusion gained further support from the notion that the expression of the pht4;6 gene is, in contrast to genes coding for major phosphate importers, substantially induced by tZ. Taken together, our findings point to a critical function of PHT4;6 to control cellular phosphate levels, in particular the cytosolic Pi availability, required to energize plant primary metabolism for proper plant development. Phosphate and its allocation mediated by PHT4;6 is critical to prevent onset of dark-induced senescence. PMID:27325894

Ground-level ozone (O3) concentrations are expected to increase over the 21(st) century, especially in East Asia. However, the impact of O3 has not been directly assessed at the forest level in this region. We performed O3 flux-based risk assessments of carbon sequestration capacity in an old cool temperate deciduous forest, consisting of O3-sensitive Japanese beech (Fagus crenata), and in a warm temperate deciduous and evergreen forest dominated by O3-tolerant Konara oak (Quercus serrata) based on long-term CO2 flux observations. On the basis of a practical approach for a continuous estimation of canopy-level stomatal conductance (Gs), higher phytotoxic ozone dose above a threshold of 0 uptake (POD0) with higher Gs was observed in the beech forest than that in the oak forest. Light-saturated gross primary production, as a measure of carbon sequestration capacity of forest ecosystem, declined earlier in the late growth season with increasing POD0, suggesting an earlier autumn senescence, especially in the O3-sensitive beech forest, but not in the O3-tolerant oak forest. PMID:27601188

Ground-level ozone (O3) concentrations are expected to increase over the 21st century, especially in East Asia. However, the impact of O3 has not been directly assessed at the forest level in this region. We performed O3 flux-based risk assessments of carbon sequestration capacity in an old cool temperate deciduous forest, consisting of O3-sensitive Japanese beech (Fagus crenata), and in a warm temperate deciduous and evergreen forest dominated by O3-tolerant Konara oak (Quercus serrata) based on long-term CO2 flux observations. On the basis of a practical approach for a continuous estimation of canopy-level stomatal conductance (Gs), higher phytotoxic ozone dose above a threshold of 0 uptake (POD0) with higher Gs was observed in the beech forest than that in the oak forest. Light-saturated gross primary production, as a measure of carbon sequestration capacity of forest ecosystem, declined earlier in the late growth season with increasing POD0, suggesting an earlier autumn senescence, especially in the O3-sensitive beech forest, but not in the O3-tolerant oak forest. PMID:27601188

Leaf senescence is not a passive degenerative process; it represents a process of nutrient relocation, in which materials are salvaged for growth at a later stage or to produce the next generation. Leaf senescence is regulated by various factors, such as darkness, stress, aging, and phytohormones. Strigolactone is a recently identified phytohormone, and it has multiple functions in plant development, including repression of branching. Although strigolactone is implicated in the regulation of leaf senescence, little is known about its molecular mechanism of action. In this study, strigolactone biosynthesis mutant strains of Arabidopsis (Arabidopsis thaliana) showed a delayed senescence phenotype during dark incubation. The strigolactone biosynthesis genes MORE AXIALLY GROWTH3 (MAX3) and MAX4 were drastically induced during dark incubation and treatment with the senescence-promoting phytohormone ethylene, suggesting that strigolactone is synthesized in the leaf during leaf senescence. This hypothesis was confirmed by a grafting experiment using max4 as the stock and Columbia-0 as the scion, in which the leaves from the Columbia-0 scion senesced earlier than max4 stock leaves. Dark incubation induced the synthesis of ethylene independent of strigolactone. Strigolactone biosynthesis mutants showed a delayed senescence phenotype during ethylene treatment in the light. Furthermore, leaf senescence was strongly accelerated by the application of strigolactone in the presence of ethylene and not by strigolactone alone. These observations suggest that strigolactone promotes leaf senescence by enhancing the action of ethylene. Thus, dark-induced senescence is regulated by a two-step mechanism: induction of ethylene synthesis and consequent induction of strigolactone synthesis in the leaf. PMID:25979917

Cellularsenescence is the state of permanent inhibition of cell proliferation. Replicative senescence occurs due to the end replication problem and shortening telomeres with each cell division leading to DNA damage response (DDR). The number of short telomeres increases with age and age-related pathologies. Stress induced senescence, although not accompanied by attrition of telomeres, is also attributed to the DDR induced by irreparable DNA lesions in telomeric DNA. Senescent cells characterized by the presence of γH2AX, the common marker of double DNA strand breaks, and other senescence markers including activity of SA-β-gal, accumulate in tissues of aged animals and humans as well as at sites of pathology. It is believed that cellularsenescence evolved as a cancer barrier since non-proliferating senescent cells cannot be transformed to neoplastic cells. On the other hand senescent cells favor cancer development, just like other age-related pathologies, by creating a low grade inflammatory state due to senescence associated secretory phenotype (SASP). Reversal/inhibition of cellularsenescence could prolong healthy life span, thus many attempts have been undertaken to influence cellularsenescence. The two main approaches are genetic and pharmacological/nutritional modifications of cell fate. The first one concerns cell reprogramming by induced pluripotent stem cells (iPSCs), which in vitro is effective even in cells undergoing senescence, or derived from very old or progeroid patients. The second approach concerns modification of senescence signaling pathways just like TOR-induced by pharmacological or with natural agents. However, knowing that aging is unavoidable we cannot expect its elimination, but prolonging healthy life span is a goal worth serious consideration. PMID:23064316

Research into extreme drought tolerance in resurrection plants using species such as Craterostigma plantagineum, C. wilmsii, Xerophyta humilis, Tortula ruralis, and Sporobolus stapfianus has provided some insight into the desiccation tolerance mechanisms utilized by these plants to allow them to persist under extremely adverse environmental conditions. Some of the mechanisms used to ensure cellular preservation during severe dehydration appear to be peculiar to resurrection plants. Apart from the ability to preserve vital cellular components during drying and rehydration, such mechanisms include the ability to down-regulate growth-related metabolism rapidly in response to changes in water availability, and the ability to inhibit dehydration-induced senescence programs enabling reconstitution of photosynthetic capacity quickly following a rainfall event. Extensive research on the molecular mechanism of leaf senescence in non-resurrection plants has revealed a multi-layered regulatory network operates to control programed cell death pathways. However, very little is known about the molecular mechanisms that resurrection plants employ to avoid undergoing drought-related senescence during the desiccation process. To survive desiccation, dehydration in the perennial resurrection grass S. stapfianus must proceed slowly over a period of 7 days or more. Leaves detached from the plant before 60% relative water content (RWC) is attained are desiccation-sensitive indicating that desiccation tolerance is conferred in vegetative tissue of S. stapfianus when the leaf RWC has declined to 60%. Whilst some older leaves remaining attached to the plant during dehydration will senesce, suggesting dehydration-induced senescence may be influenced by leaf age or the rate of dehydration in individual leaves, the majority of leaves do not senesce. Rather these leaves dehydrate to air-dryness and revive fully following rehydration. Hence it seems likely that there are genes expressed in

Myeloperoxidase (MPO)-derived product hypochlorous acid (HOCl) is able to induce cellularsenescence and MPO is also expressed in endothelial cells besides the well-recognized immune cells. This study aims to clarify the association of endothelium-derived MPO with endothelial senescence in hyperlipidemia. The rats were fed with high-fat diet for 8 weeks to establish a hyperlipidemic model, which showed an increase in plasma lipids, endothelium-derived MPO expression, endothelial senescence and endothelial dysfunction concomitant with a reduction in glycogen synthase kinase 3 beta (GSK-3β) activity and phosphorylated β-catenin (p-β-catenin) level as well as an increase in β-catenin and p53 levels within the endothelium. Next, human umbilical vein endothelial cells (HUVECs) were incubated with oxidized low density lipoprotein (ox-LDL, 100 μg/ml) for 24 h to establish a senescent cell model in vitro. Consistent with the finding in vivo, ox-LDL-induced MPO expression and HUVECs senescence, accompanied by a decrease in GSK-3β activity and p-β-catenin level as well as an increase in HOCl content, β-catenin and p53 levels; these phenomena were attenuated by MPO inhibitor. Replacement of ox-LDL with HOCl could also induce HUVECs senescence and activate the β-catenin/p53 pathway. Based on these observations, we conclude that endothelium-derived MPO is upregulated in hyperlipidemic rats, which may contribute to the accelerated vascular endothelial senescence through a mechanism involving the β-catenin/p53 pathway. PMID:26474698

Cellularsenescence is a process by which cells enter a state of permanent cell cycle arrest. It is commonly believed to underlie organismal aging and age-associated diseases. However, the mechanism by which cellularsenescence contributes to aging and age-associated pathologies remains unclear. Recent studies showed that senescent cells exert detrimental effects on the tissue microenvironment, generating pathological facilitators or aggravators. The most significant environmental effector resulting from senescent cells is the senescence-associated secretory phenotype (SASP), which is constituted by a strikingly increased expression and secretion of diverse pro-inflammatory cytokines. Careful investigation into the components of SASPs and their mechanism of action, may improve our understanding of the pathological backgrounds of age-associated diseases. In this review, we focus on the differential expression of SASP-related genes, in addition to SASP components, during the progress of senescence. We also provide a perspective on the possible action mechanisms of SASP components, and potential contributions of SASP-expressing senescent cells, to age-associated pathologies. [BMB Reports 2015; 48(10): 549-558] PMID:26129674

The term cellularsenescence was introduced more than five decades ago to describe the state of growth arrest observed in aging cells. Since this initial discovery, the phenotypes associated with cellularsenescence have expanded beyond growth arrest to include alterations in cellular metabolism, secreted cytokines, epigenetic regulation and protein expression. Recently, senescence has been shown to play an important role in vivo not only in relation to aging, but also during embryonic development. Thus, cellularsenescence serves different purposes and comprises a wide range of distinct phenotypes across multiple cell types. Whether all cell types, including post-mitotic neurons, are capable of entering into a senescent state remains unclear. In this review we examine recent data that suggest that cellularsenescence plays a role in brain aging and, notably, may not be limited to glia but also neurons. We suggest that there is a high level of similarity between some of the pathological changes that occur in the brain in Alzheimer's and Parkinson's diseases and those phenotypes observed in cellularsenescence, leading us to propose that neurons and glia can exhibit hallmarks of senescence previously documented in peripheral tissues. PMID:25305051

The term cellularsenescence was introduced more than five decades ago to describe the state of growth arrest observed in aging cells. Since this initial discovery, the phenotypes associated with cellularsenescence have expanded beyond growth arrest to include alterations in cellular metabolism, secreted cytokines, epigenetic regulation and protein expression. Recently, senescence has been shown to play an important role in vivo not only in relation to aging, but also during embryonic development. Thus, cellularsenescence serves different purposes and comprises a wide range of distinct phenotypes across multiple cell types. Whether all cell types, including post-mitotic neurons, are capable of entering into a senescent state remains unclear. In this review we examine recent data that suggest that cellularsenescence plays a role in brain aging and, notably, may not be limited to glia but also neurons. We suggest that there is a high level of similarity between some of the pathological changes that occur in the brain in Alzheimer’s and Parkinson’s diseases and those phenotypes observed in cellularsenescence, leading us to propose that neurons and glia can exhibit hallmarks of senescence previously documented in peripheral tissues. PMID:25305051

Graphene oxide (GO) consisting of a carbon monolayer has been widely investigated for tissue engineering platforms because of its unique properties. For this study, we fabricated a GO-applied scaffold and assessed the cellular and tissue behaviors in the scaffold. A preclinical test was conducted to ascertain whether the GO scaffold promoted bone induction in dog tooth extraction sockets. For this study, GO scaffolds were prepared by coating the surface of a collagen sponge scaffold with 0.1 and 1 µg/mL GO dispersion. Scaffolds were characterized using scanning electron microscopy (SEM), physical testing, cell seeding, and rat subcutaneous implant testing. Then a GO scaffold was implanted into a dog tooth extraction socket. Histological observations were made at 2 weeks postsurgery. SEM observations show that GO attached to the surface of collagen scaffold struts. The GO scaffold exhibited an interconnected structure resembling that of control subjects. GO application improved the physical strength, enzyme resistance, and adsorption of calcium and proteins. Cytocompatibility tests showed that GO application significantly increased osteoblastic MC3T3-E1 cell proliferation. In addition, an assessment of rat subcutaneous tissue response revealed that implantation of 1 µg/mL GO scaffold stimulated cellular ingrowth behavior, suggesting that the GO scaffold exhibited good biocompatibility. The tissue ingrowth area and DNA contents of 1 µg/mL GO scaffold were, respectively, approximately 2.5-fold and 1.4-fold greater than those of the control. Particularly, the infiltration of ED2-positive (M2) macrophages and blood vessels were prominent in the GO scaffold. Dog bone-formation tests showed that 1 µg/mL GO scaffold implantation enhanced bone formation. New bone formation following GO scaffold implantation was enhanced fivefold compared to that in control subjects. These results suggest that GO was biocompatible and had high bone-formation capability for the scaffold

Chronic obstructive pulmonary disease (COPD) is a major disease of the lungs. It primarily occurs after a prolonged period of cigarette smoking. Chronic inflammation of airways and the alveolar space as well as lung tissue destruction are the hallmarks of COPD. Recently it has been shown that cellularsenescence might play a role in the pathogenesis of COPD. Cellularsenescence comprises signal transduction program, leading to irreversible cell cycle arrest. The growth arrest in senescence can be triggered by many different mechanisms, including DNA damage and its recognition by cellular sensors, leading to the activation of cell cycle checkpoint responses and activation of DNA repair machinery. Senescence can be induced by several genotoxic factors apart from telomere attrition. When senescence induction is based on DNA damage, senescent cells display a unique phenotype, which has been termed "senescence-associated secretory phenotype" (SASP). SASP may be an important driver of chronic inflammation and therefore may be part of a vicious cycle of inflammation, DNA damage, and senescence. This research perspective aims to showcase cellularsenescence with relevance to COPD and the striking similarities between the mediators and secretory phenotype in COPD and SASP. PMID:25171460

Somatic cells senesce in culture after a finite number of divisions indefinitely arresting their proliferation. DNA damage and senescence increase the cellular number of centrosomes, the 2 microtubule organizing centers that ensure bipolar mitotic spindles. Centrosomes also provide the basal body from which primary cilia extend to sense and transduce various extracellular signals, notably Hedgehog. Primary cilium formation is facilitated by cellular quiescence a temporary cell cycle exit, but the impact of senescence on cilia is unknown. We found that senescent human fibroblasts have increased frequency and length of primary cilia. Levels of the negative ciliary regulator CP110 were reduced in senescent cells, as were levels of key elements of the Hedgehog pathway. Hedgehog inhibition reduced proliferation in young cells with increased cilium length accompanying cell cycle arrest suggesting a regulatory function for Hedgehog in primary ciliation. Depletion of CP110 in young cell populations increased ciliation frequencies and reduced cell proliferation. These data suggest that primary cilia are potentially novel determinants of the reduced cellular proliferation that initiates senescence. PMID:25486364

Somatic cells senesce in culture after a finite number of divisions indefinitely arresting their proliferation. DNA damage and senescence increase the cellular number of centrosomes, the 2 microtubule organizing centers that ensure bipolar mitotic spindles. Centrosomes also provide the basal body from which primary cilia extend to sense and transduce various extracellular signals, notably Hedgehog. Primary cilium formation is facilitated by cellular quiescence a temporary cell cycle exit, but the impact of senescence on cilia is unknown. We found that senescent human fibroblasts have increased frequency and length of primary cilia. Levels of the negative ciliary regulator CP110 were reduced in senescent cells, as were levels of key elements of the Hedgehog pathway. Hedgehog inhibition reduced proliferation in young cells with increased cilium length accompanying cell cycle arrest suggesting a regulatory function for Hedgehog in primary ciliation. Depletion of CP110 in young cell populations increased ciliation frequencies and reduced cell proliferation. These data suggest that primary cilia are potentially novel determinants of the reduced cellular proliferation that initiates senescence. PMID:25486364

We have tested the hypothesis that the antidiabetic biguanide metformin can be used to manipulate the threshold for stress-induced senescence (SIS), thus accelerating the onset of cancer-protective cellularsenescence in response to oncogenic stimuli. Using senescence-prone murine embryonic fibroblasts (MEFs), we assessed whether metformin treatment modified the senescence phenotype that is activated in response to DNA damaging inducers. Metformin significantly enhanced the number of MEFs entering a senescent stage in response to doxorubicin, an anthracycline that induces cell senescence by activating DNA damage signaling pathways (e.g., ATM/ATR) in a reactive oxygen species (ROS)-dependent manner. Using WI-38 and BJ-1 human diploid fibroblasts (HDFs), we explored whether metformin supplementation throughout their entire replicative lifespan may promote the early appearance of the biomarkers of replicative senescence. Chronic metformin significantly reduced HDFs' lifespan by accelerating both the loss of replicative potential and the acquisition of replicative senescence-related biomarkers (e.g., enlarged and flattened cell shapes, loss of arrayed arrangement, accumulation of intracellular and extracellular debris and SA-β-gal-positive staining). Metformin functioned as a bona fide stressful agent, inducing monotonic, dose-dependent, SIS-like responses in BJ-1 HDFs, which are highly resistant to ROS-induced premature senescence. Metformin-induced SIS in BJ-1 fibroblasts was accompanied by the striking activation of several microRNAs belonging to the miR-200s family (miR-200a, miR-141 and miR429) and miR-205, thus mimicking a recently described ability of ROS to chemosensitize cancer cells by specifically upregulating anti-EMT (epithelial-to-mesenchymal transition) miR-200s. Because the unlimited proliferative potential of stem cells results from their metabolic refractoriness to SIS, we finally tested if metformin treatment could circumvent the stress (e.g., ROS

Cellularsenescence has been recently linked to the promotion of age-related pathologies, including a decline in regenerative capacity. While such capacity deteriorates with age in mammals, it remains intact in species such as salamanders, which have an extensive repertoire of regeneration and can undergo multiple episodes through their lifespan. Here we show that, surprisingly, there is a significant induction of cellularsenescence during salamander limb regeneration, but that rapid and effective mechanisms of senescent cell clearance operate in normal and regenerating tissues. Furthermore, the number of senescent cells does not increase upon repetitive amputation or ageing, in contrast to mammals. Finally, we identify the macrophage as a critical player in this efficient senescent cell clearance mechanism. We propose that effective immunosurveillance of senescent cells in salamanders supports their ability to undergo regeneration throughout their lifespan. PMID:25942455

Cancer and senescence are both complex transformative processes that dramatically alter many features of cell physiology and their interactions with surrounding tissues. Developing the wide range of cellular features characteristic of these conditions requires profound alterations in global gene expression patterns, which can be achieved by suppressing, activating, or uncoupling cellular gene regulatory pathways. Many genes associated with the initiation and development of tumors are regulated at the level of mRNA decay, frequently through the activity of AU-rich mRNA-destabilizing elements (AREs) located in their 3′-untranslated regions. As such, cellular factors that recognize and control the decay of ARE-containing mRNAs can influence tumorigenic or senescent phenotypes mediated by products of these transcripts. In this review, we discuss evidence showing how suppressed expression and/or activity of the ARE-binding protein tristetraprolin (TTP) can contribute to these processes. Next, we outline current findings linking TTP suppression to exacerbation of individual tumorigenic phenotypes, and the roles of specific TTP substrate mRNAs in mediating these effects. Finally, we survey potential mechanisms that cells may employ to suppress TTP expression in cancer, and propose potential diagnostic and therapeutic strategies that may exploit the relationship between TTP expression and tumor progression or senescence. PMID:22387927

Mesenchymal stem cell (MSC) transplantation has the potential for organ repair. Nevertheless, some factors might lessen the regenerative potential of MSCs, e.g. donor age or systemic disease. It is thus important to carefully assess the patient's suitability for autologous MSC transplantation. Here we investigated the effects of chronic kidney disease (CKD) on MSC function. We isolated bone marrow MSCs from remnant kidney rats (RK) with CKD (CKD-RK-MSC) and found signs of premature senescence: spontaneous adipogenesis, reduced proliferation capacity, active senescence-associated-β-galactosidase, accumulation of actin and a modulated secretion profile. The functionality of CKD-RK-MSCs in vivo was tested in rats with acute anti-Thy1.1-nephritis, where healthy MSCs have been shown to be beneficial. Rats received healthy MSCs, CKD-RK-MSC or medium by injection into the left renal artery. Kidneys receiving healthy MSCs exhibited accelerated healing of glomerular lesions, whereas CKD-RK-MSC or medium exerted no benefit. The negative influence of advanced CKD/uremia on MSCs was confirmed in a second model of CKD, adenine nephropathy (AD). MSCs from rats with adenine nephropathy (CKD-AD-MSC) also exhibited cellular modifications and functional deficits in vivo. We conclude that CKD leads to a sustained loss of in vitro and in vivo functionality in MSCs, possibly due to premature cellularsenescence. Considering autologous MSC therapy in human renal disease, studies identifying uremia-associated mechanisms that account for altered MSC function are urgently needed. PMID:24667162

Light regulates leaf senescence and light deprivation causes large-scale transcriptional reprogramming to dismantle cellular components and remobilize nutrients to sink organs, such as seeds and storage tissue. We recently reported that in Arabidopsis (Arabidopsis thaliana), Phytochrome-Interacting Factor4 (PIF4) and PIF5 promote dark-induced senescence and natural senescence by directly activating the expression of typical senescence-associated genes (SAGs), including ORESARA1 (ORE1) and ETHYLENE INSENSITIVE3 (EIN3). In contrast, phytochrome B (PhyB) inhibits leaf senescence by repressing PIF4 and PIF5 at the post-translational level. Although we found how red light signaling represses leaf senescence in Arabidopsis, it remains unknown whether PhyB and/or PhyA are involved in leaf senescence in rice (Oryza sativa). Here we show that rice phyB knockout mutants (osphyB-1, -2, and -3) exhibited an early senescence phenotype during dark-induced senescence, but an osphyA knockout mutant (osphyA-3) senesced normally. The RT-qPCR analysis revealed that several senescence-associated genes, including OsORE1 and OsEIN3, were significantly up-regulated in osphyB-2 mutants, indicating that OsPhyB also inhibits leaf senescence, like Arabidopsis PhyB. We also found that leaf segments of osphyB-2 senesced faster even under light conditions. Supplementation with nitrogen compounds, such as KNO3 and NH4NO3, rescued the early senescence phenotype of osphyB-2, indicating that starvation is one of the major signaling factors in the OsPhyB-dependent leaf senescence pathway. PMID:27135344

Growth differentiation factor 15 (GDF15) is an emerging biomarker of cardiovascular risk and disease. Microarray analyses revealed that GDF15 levels were increased during cellularsenescence induced by ionizing radiation (IR) in human aortic endothelial cells (HAECs). However, the role of GDF15 in HAEC cellularsenescence remains unclear. This study demonstrated that downregulation of GDF15 in HAECs partially prevented cellularsenescence triggered by IR, which was confirmed by recovery of cell proliferation and reverse senescence-associated β-galactosidase (SA-β-gal) staining. Conversely, upregulation of GDF15-induced cellularsenescence in HAECs, confirmed by G0/G1 cell cycle arrest, decreased during cell proliferation and increased SA-β-gal staining. GDF15-induced cellularsenescence was observed in p16-knockdown cells but not in p53-knockdown cells. GDF15 expression in endothelial cells also generated reactive oxygen species (ROS), which led to activation of extracellular signal-regulated kinases (ERKs) and induction of senescence by oxidative stress. These results suggested that GDF15 might play an important role in cellularsenescence through a ROS-mediated p16 pathway and contribute to the pathogenesis of atherosclerosis via pro-senescent activity. PMID:26909594

Growth differentiation factor 15 (GDF15) is an emerging biomarker of cardiovascular risk and disease. Microarray analyses revealed that GDF15 levels were increased during cellularsenescence induced by ionizing radiation (IR) in human aortic endothelial cells (HAECs). However, the role of GDF15 in HAEC cellularsenescence remains unclear. This study demonstrated that downregulation of GDF15 in HAECs partially prevented cellularsenescence triggered by IR, which was confirmed by recovery of cell proliferation and reverse senescence-associated β-galactosidase (SA-β-gal) staining. Conversely, upregulation of GDF15-induced cellularsenescence in HAECs, confirmed by G0/G1 cell cycle arrest, decreased during cell proliferation and increased SA-β-gal staining. GDF15-induced cellularsenescence was observed in p16-knockdown cells but not in p53-knockdown cells. GDF15 expression in endothelial cells also generated reactive oxygen species (ROS), which led to activation of extracellular signal-regulated kinases (ERKs) and induction of senescence by oxidative stress. These results suggested that GDF15 might play an important role in cellularsenescence through a ROS-mediated p16 pathway and contribute to the pathogenesis of atherosclerosis via pro-senescent activity. PMID:26909594

The initiation, progression, and natural variation of autumn senescence in European aspen (Populus tremula) was investigated by monitoring chlorophyll degradation in (1) trees growing in natural stands and (2) cloned trees growing in a greenhouse under various light regimes. The main trigger for the initiation of autumn senescence in aspen is the shortening photoperiod, but there was a large degree of variation in the onset of senescence, both within local populations and among trees originating from different populations, where it correlated with the latitude of their respective origins. The variation for onset of senescence with a population was much larger than the variation of bud set. Once started, autumn senescence was accelerated by low temperature and longer nights, and clones that started to senescence late had a faster senescence. Bud set and autumn senescence appeared to be under the control of two independent critical photoperiods, but senescence could not be initiated until a certain time after bud set, suggesting that bud set and growth arrest are important for the trees to acquire competence to respond to the photoperiodic trigger to undergo autumn senescence. A timetable of events related to bud set and autumn senescence is presented. PMID:19201914

Bangle (Zingiber purpureum) is a tropical ginger that is used as a spice in Southeast Asia. Phenylbutenoid dimers isolated from Bangle have exhibited neurotrophic effects in primary cultured rat cortical neurons and PC12 cells. Furthermore, chronic treatment with phenylbutenoid dimers enhances hippocampal neurogenesis in olfactory bulbectomized mice. In this study, we investigated the effects of Bangle extract on behavior and hippocampal neurogenesis in vivo. SAMP8 mice, which are an established model for accelerated aging, with age-related learning and memory impairments, were given a Bangle-containing diet for 1 month, and subsequent behavioral tests and immunohistochemistry for Ki67, a proliferating cell marker, were performed. We found that the Bangle-containing diet improved spatial learning and memory deficits in the Morris water maze and significantly increased the numbers of Ki67-positive cells in the dentate gyrus of the SAMP8 mice. In addition, the Bangle extract exhibited a neurotrophin-like activity as indicated by the induction of neurite sprouting in PC12 cells. Our results suggest that Bangle is beneficial for the prevention of age-related progression of cognitive impairment. PMID:26829513

This paper proposes a real-time feature extraction VLSI architecture for high-resolution images based on the accelerated KAZE algorithm. Firstly, a new system architecture is proposed. It increases the system throughput, provides flexibility in image resolution, and offers trade-offs between speed and scaling robustness. The architecture consists of a two-dimensional pipeline array that fully utilizes computational similarities in octaves. Secondly, a substructure (block-serial discrete-time cellular neural network) that can realize a nonlinear filter is proposed. This structure decreases the memory demand through the removal of data dependency. Thirdly, a hardware-friendly descriptor is introduced in order to overcome the hardware design bottleneck through the polar sample pattern; a simplified method to realize rotation invariance is also presented. Finally, the proposed architecture is designed in TSMC 65 nm CMOS technology. The experimental results show a performance of 127 fps in full HD resolution at 200 MHz frequency. The peak performance reaches 181 GOPS and the throughput is double the speed of other state-of-the-art architectures. PMID:26404305

This paper proposes a real-time feature extraction VLSI architecture for high-resolution images based on the accelerated KAZE algorithm. Firstly, a new system architecture is proposed. It increases the system throughput, provides flexibility in image resolution, and offers trade-offs between speed and scaling robustness. The architecture consists of a two-dimensional pipeline array that fully utilizes computational similarities in octaves. Secondly, a substructure (block-serial discrete-time cellular neural network) that can realize a nonlinear filter is proposed. This structure decreases the memory demand through the removal of data dependency. Thirdly, a hardware-friendly descriptor is introduced in order to overcome the hardware design bottleneck through the polar sample pattern; a simplified method to realize rotation invariance is also presented. Finally, the proposed architecture is designed in TSMC 65 nm CMOS technology. The experimental results show a performance of 127 fps in full HD resolution at 200 MHz frequency. The peak performance reaches 181 GOPS and the throughput is double the speed of other state-of-the-art architectures. PMID:26404305

The distinction between senescent and non-senescent mortality proves to be very valuable for describing and analyzing age patterns of death rates. Unfortunately, standard methods for estimating these mortality components are lacking. The first part of this study discusses alternative methods for estimating background and senescent mortality among adults and proposes a simple approach based on death rates by causes of death. The second part examines trends in senescent life expectancy (i.e. the life expectancy implied by senescent mortality) and compares them with trends in conventional longevity indicators between 1960 and 2000 in a group of 17 developed countries with low mortality. Senescent life expectancy for females rises at an average rate of 1.54 years per decade between 1960 and 2000 in these countries. The shape of the distribution of senescent deaths by age remains relatively invariant while the entire distribution shifts over time to higher ages as longevity rose. PMID:19851933

Fibroblasts have been extensively used as a model to study cellularsenescence. The purpose of this study was to investigate whether the human foreskin fibroblast aging process could be regulated by using the biomaterial chitosan. Fibroblasts cultured on commercial tissue culture polystyrene (TCPS) entered senescence after 55–60 population doublings (PDs), and were accompanied by larger cell shape, higher senescence-associated β-galactosidase (SA β-gal) activity, lower proliferation capacity, and upregulation of senescence-associated molecular markers p21, p53, retinoblastoma (pRB), and p16. Before senescence was reached, PD48 cells were collected from TCPS and seeded on chitosan for three days (PD48-Cd3) to form multicellular spheroids. The protein expression of senescence-associated secretory phenotypes (SASPs) and senescence-associated molecular markers of these cells in PD48-Cd3 spheroids were downregulated significantly. Following chitosan treatment, fibroblasts reseeded on TCPS showed lower SA β-gal activity, increased cellular motility, and a higher proliferation ability of 70–75 PDs. These phenotypic changes were not accompanied by colonies forming in soft agar and a continuous decrease in the senescence-associated proteins p53 and pRB which act as a barrier to tumorigenesis. These results demonstrate that chitosan treatment could delay the induction of senescence which may be useful and safe for future tissue engineering applications. PMID:26465338

Cellularsenescence or cellular aging, defined by permanent cell cycle arrest, is well known for its evolutionary advantage in protecting the organism from developing cancer; however, it is also acknowledged that aged stromal cells can significantly expedite epithelial tumorigenesis, although exactly how they function to augment tumor formation remains elusive. Recent evidence suggests that this tumor-promoting effect is likely mediated by diffusible pro-inflammatory molecules synthesized and released by senescent stromal fibroblasts, acting in a paracrine fashion on adjacent tumor epithelium. Mobilization of the inflammatory network by senescent fibroblasts has bifurcated roles on the epithelial and stromal compartments, converging on the promotion of epithelial tumorigenesis. A thorough understanding of the regulatory mechanisms underlying these events may lead to improved approaches in cancer treatment. PMID:19273333

Mitochondria are central regulators of energy homeostasis and may play a pivotal role in mechanisms of cellularsenescence and age-related neurodegenerative and metabolic disorders. However, mitochondrial bioenergetic parameters have not been systematically evaluated under identi...

Aging is the major risk factor per se for the development of cardiovascular diseases. The senescence of the endothelial cells (ECs) that line the lumen of blood vessels is the cellular basis for these age-dependent vascular pathologies, including atherosclerosis and hypertension. During their lifespan, ECs may reach a stage of senescence by two different pathways; a replicative one derived from their preprogrammed finite number of cell divisions; and one induced by stress stimuli. Also, certain physiological stimuli, such as transforming growth factor-β, are able to modulate cellularsenescence. Currently, the cellular aging process is being widely studied to identify novel molecular markers whose changes correlate with senescence. This review focuses on the regulation of alternative splicing mediated by the serine-arginine splicing factor 1 (SRSF1, or ASF/SF2) during endothelial senescence, a process that is associated with a differential subcellular localization of SRSF1, which typically exhibits a scattered distribution throughout the cytoplasm. Based on its senescence-dependent involvement in alternative splicing, we postulate that SRSF1 is a key marker of EC senescence, regulating the expression of alternative isoforms of target genes such as endoglin (ENG), vascular endothelial growth factor A (VEGFA), tissue factor (T3), or lamin A (LMNA) that integrate in a common molecular senescence program. PMID:22470345

Sirtuin family members with lysine deacetylase activity are known to play an important role in anti-aging and longevity. Cellularsenescence is one of the hallmarks of aging, and downregulation of sirtuin is reported to induce premature senescence. In this study, we investigated the effects of small-molecule sirtuin inhibitors on cellularsenescence. Various small molecules such as tenovin-1 and EX527 were employed for direct sirtuin activity inhibition. U251, SNB-75, and U87MG glioblastoma cells treated with sirtuin inhibitors exhibited phenotypes with nuclear enlargement. Furthermore, treatment of rat primary astrocytes with tenovin-1 also increased the size of the nucleus. The activity of senescence-associated β-galactosidase, a marker of cellularsenescence, was induced by tenovin-1 and EX527 treatment in U87MG glioblastoma cells. Consistent with the senescent phenotype, treatment with tenovin-1 increased p53 expression in U87MG cells. This study demonstrated the senescence-inducing effect of sirtuin inhibitors, which are potentially useful tools for senescence research. PMID:27340387

Sirtuin family members with lysine deacetylase activity are known to play an important role in anti-aging and longevity. Cellularsenescence is one of the hallmarks of aging, and downregulation of sirtuin is reported to induce premature senescence. In this study, we investigated the effects of small-molecule sirtuin inhibitors on cellularsenescence. Various small molecules such as tenovin-1 and EX527 were employed for direct sirtuin activity inhibition. U251, SNB-75, and U87MG glioblastoma cells treated with sirtuin inhibitors exhibited phenotypes with nuclear enlargement. Furthermore, treatment of rat primary astrocytes with tenovin-1 also increased the size of the nucleus. The activity of senescence-associated β-galactosidase, a marker of cellularsenescence, was induced by tenovin-1 and EX527 treatment in U87MG glioblastoma cells. Consistent with the senescent phenotype, treatment with tenovin-1 increased p53 expression in U87MG cells. This study demonstrated the senescence-inducing effect of sirtuin inhibitors, which are potentially useful tools for senescence research. PMID:27340387

Objectives Cellularsenescence is a state of irreversible growth arrest induced either by telomere shortening (replicative senescence) or stress. The bronchial epithelial cell is often injured by inhaled toxic substances, such as cigarette smoke. In the present study, we investigated whether exposure to cigarette smoke extract (CSE) induces senescence of bronchial epithelial cells; and Cordyceps sinensis mechanism of inhibition of CSE-induced cellularsenescence. Methods Human bronchial epithelial cells (16HBE cells) cultured in vitro were treated with CSE and/or C. sinensis. p16, p21, and senescence-associated-galactosidase activity were used to detect cellularsenescence with immunofluorescence, quantitative polymerase chain reaction, and Western blotting. Reactive oxygen species (ROS), PI3K/AKT/mTOR and their phosphorylated proteins were examined to testify the activation of signaling pathway by ROS fluorescent staining and Western blotting. Then, inhibitors of ROS and PI3K were used to further confirm the function of this pathway. Results Cellularsenescence was upregulated by CSE treatment, and C. sinensis can decrease CSE-induced cellularsenescence. Activation of ROS/PI3K/AKT/mTOR signaling pathway was enhanced by CSE treatment, and decreased when C. sinensis was added. Blocking ROS/PI3K/AKT/mTOR signaling pathway can attenuate CSE-induced cellularsenescence. Conclusion CSE can induce cellularsenescence in human bronchial epithelial cells, and ROS/PI3K/AKT/mTOR signaling pathway may play an important role in this process. C. sinensis can inhibit the CSE-induced senescence. PMID:27555762

A hallmark trait of cellularsenescence is the acquisition of a senescence-associated secretory phenotype (SASP). SASP factors include cytokines and their receptors (IL-6, IL-8, osteoprotegerin, GM-CSF), chemokines and their ligands (MCP-1, HCC4), and oncogenes (Gro1 and Gro2), many of them encoded by mRNAs whose stability and translation are tightly regulated. Using two models of human fibroblast senescence (WI-38 and IDH4 cells), we report the identification of RNA-binding protein NF90 as a post-transcriptional repressor of several SASP factors. In ‘young’, proliferating fibroblasts, NF90 was highly abundant, associated with numerous SASP mRNAs, and inhibited their expression. By contrast, senescent cells expressed low levels of NF90, thus allowing SASP factor expression to increase. NF90 elicited these effects mainly by repressing the translation of target SASP mRNAs, since silencing NF90 did not increase the steady-state levels of SASP mRNAs but elevated key SASP factors including MCP-1, GROa, IL-6, and IL-8. Our findings indicate that NF90 contributes to maintaining low levels of SASP factors in non-senescent cells, while NF90 reduction in senescent cells allows SASP factor expression to rise. PMID:23117626

Recent studies have demonstrated that the accumulation of senescent endothelial cells may be the primary cause of cardiovascular diseases. Because of their multifunctional properties, endothelial cells actively take part in stimulating the immune system and inflammation. In addition, ageing is characterized by the progressive deterioration of immune cells and a decline in the activation of the immune response. This results in a loss of the primary function of the immune system, which is eliminating damaged/senescent cells and neutralizing potential sources of harmful inflammatory reactions. In this review, we discuss cellularsenescence and the senescence-associated secretory phenotype (SASP) of endothelial cells and summarize the link between endothelial cells and immunosenescence. We describe the possibility that age-related changes in Toll-like receptors (TLRs) and microRNAs can affect the phenotypes of senescent endothelial cells and immune cells via a negative feedback loop aimed at restraining the excessive pro-inflammatory response. This review also addresses the following questions: how do senescent endothelial cells influence ageing or age-related changes in the inflammatory burden; what is the connection between ECs and immunosenescence, and what are the crucial hypothetical pathways linking endothelial cells and the immune system during ageing. PMID:27235855

Cellularsenescence is a complex stress response that leads to an irreversible state of cell growth arrest. Senescence may be induced by various stimuli such as telomere shortening, DNA damage or oncogenic insult, among others. Senescent cells are metabolically highly active, producing a wealth of cytokines and chemokines that, depending on the context, may have a beneficial or deleterious effect on the organism. Senescence is considered a tightly regulated stress response that is largely governed by the p53/p21 and p16/Rb pathways. Many molecules have been identified as regulators of these two networks, such as transcription factors, chromatin modifiers and non-coding RNAs. The expression level of several long non-coding RNAs is affected during different types of senescence; however, which of these are important for the biological function remains poorly understood. Here we review our current knowledge of the mechanistic roles of lncRNAs affecting the main senescence pathways, and discuss the importance of identifying new regulators. PMID:26866709

Over time and repeated asexual divisions, many ciliate species display the characteristics of senescence, reduced fecundity and increased mortality. Their only path to recovery is sexual conjugation or autogamy. While more traditional models of cellular aging have been proposed, one of the most accepted explanations relies on the faulty mechanism by which ciliates duplicate their somatic nucleus, a process referred to as amitosis. Amitosis involves the random segregation of chromosomes with no consideration for homology. Over subsequent divisions, chromosome copy numbers will fluctuate until an entire chromosome is lost, resulting in death. Via simulations of this process, we find that senescence and death via chromosome loss is not the only possible result of amitosis. Random chromosome loss is less damaging to populations than previously thought, and strict adherence to the model predicts that Paramecium tetraurelia would not senesce. A combination of the reciprocal nature of amitosis and lethal selection against low-copy number chromosomes is responsible for this startling prediction. Additionally, our results provide an alternate explanation to recent evidence for selection on chromosome copy number in Tetrahymena thermophila and peculiar patterns of senescence in Tetrahymena pyriformis. PMID:25840368

In the presence of exogenous mortality risks, future reproduction by an individual is worth less than present reproduction to its fitness. Senescent aging thus results inevitably from transferring net fertility into younger ages. Some long-lived organisms appear to defy theory, however, presenting negligible senescence (e.g., hydra) and extended lifespans (e.g., Bristlecone Pine). Here, we investigate the possibility that the onset of vitality loss can be delayed indefinitely, even accepting the abundant evidence that reproduction is intrinsically costly to survival. For an environment with constant hazard, we establish that natural selection itself contributes to increasing density-dependent recruitment losses. We then develop a generalized model of accelerating vitality loss for analyzing fitness optima as a tradeoff between compression and spread in the age profile of net fertility. Across a realistic spectrum of senescent age profiles, density regulation of recruitment can trigger runaway selection for ever-reducing senescence. This novel prediction applies without requirement for special life-history characteristics such as indeterminate somatic growth or increasing fecundity with age. The evolution of nonsenescence from senescence is robust to the presence of exogenous adult mortality, which tends instead to increase the age-independent component of vitality loss. We simulate examples of runaway selection leading to negligible senescence and even intrinsic immortality. PMID:18166075

The aim of this study was to analyze whether polyamine (PA) metabolism is involved in dark-induced Hordeum vulgare L. ‘Nagrad’ leaf senescence. In the cell, the titer of PAs is relatively constant and is carefully controlled. Senescence-dependent increases in the titer of the free PAs putrescine, spermidine, and spermine occurred when the process was induced, accompanied by the formation of putrescine conjugates. The addition of the anti-senescing agent cytokinin, which delays senescence, to dark-incubated leaves slowed the senescence-dependent PA accumulation. A feature of the senescence process was initial accumulation of PAs at the beginning of the process and their subsequent decrease during the later stages. Indeed, the process was accompanied by both enhanced expression of PA biosynthesis and catabolism genes and an increase in the activity of enzymes involved in the two metabolic pathways. To confirm whether the capacity of the plant to control senescence might be linked to PA, chlorophyll fluorescence parameters, and leaf nitrogen status in senescing barley leaves were measured after PA catabolism inhibition and exogenously applied γ-aminobutyric acid (GABA). The results obtained by blocking putrescine oxidation showed that the senescence process was accelerated. However, when the inhibitor was applied together with GABA, senescence continued without disruption. On the other hand, inhibition of spermidine and spermine oxidation delayed the process. It could be concluded that in dark-induced leaf senescence, the initial accumulation of PAs leads to facilitating their catabolism. Putrescine supports senescence through GABA production and spermidine/spermine supports senescence-dependent degradation processes, is verified by H2O2 generation. PMID:26779231

Maize (Zea mays, L.) plants were exposed intermittently to O(3), HF or both pollutants and the progression of foliar senescence was followed by measuring chlorophyll loss, membrane breakdown and changes in stomatal conductance. At concentrations insufficient to cause foliar symptoms (0.06 microl O(3) litre(-1) and 1.0 microg Fm(-3)), exposures to HF had little or no effect, whereas O(3) exposures accelerated the rate of senescence. The rapid rate of senescence produced by O(3) was moderated if the plants were also exposed to HF. Topical application of 6-benzyladenine (BA) prior to pollutant exposures delayed senescence in all plants and completely prevented the O(3)-induced acceleration of senescence. PMID:15092310

A sharp definition of what a senescent cell is still lacking since we do not have in depth understanding of mechanisms that induce cellularsenescence. In addition, senescent cells are heterogeneous, in that not all of them express the same genes and present the same phenotype. To further clarify the classification of senescent cells, hints may be derived by the study of cellular metabolism, autophagy and proteasome activity. In this scenario, we decided to study these biological features in senescence of Mesenchymal Stromal Cells (MSC). These cells contain a subpopulation of stem cells that are able to differentiate in mesodermal derivatives (adipocytes, chondrocytes, osteocytes). In addition, they can also contribute to the homeostatic maintenance of many organs, hence, their senescence could be very deleterious for human body functions. We induced MSC senescence by oxidative stress, doxorubicin treatment, X-ray irradiation and replicative exhaustion. The first three are considered inducers of acute senescence while extensive proliferation triggers replicative senescence also named as chronic senescence. In all conditions, but replicative and high IR dose senescence, we detected a reduction of the autophagic flux, while proteasome activity was impaired in peroxide-treated and irradiated cells. Differences were observed also in metabolic status. In general, all senescent cells evidenced metabolic inflexibility and prefer to use glucose as energy fuel. Irradiated cells with low dose of X-ray and replicative senescent cells show a residual capacity to use fatty acids and glutamine as alternative fuels, respectively. Our study may be useful to discriminate among different senescent phenotypes. PMID:26540573

A sharp definition of what a senescent cell is still lacking since we do not have in depth understanding of mechanisms that induce cellularsenescence. In addition, senescent cells are heterogeneous, in that not all of them express the same genes and present the same phenotype. To further clarify the classification of senescent cells, hints may be derived by the study of cellular metabolism, autophagy and proteasome activity. In this scenario, we decided to study these biological features in senescence of Mesenchymal Stromal Cells (MSC). These cells contain a subpopulation of stem cells that are able to differentiate in mesodermal derivatives (adipocytes, chondrocytes, osteocytes). In addition, they can also contribute to the homeostatic maintenance of many organs, hence, their senescence could be very deleterious for human body functions. We induced MSC senescence by oxidative stress, doxorubicin treatment, X-ray irradiation and replicative exhaustion. The first three are considered inducers of acute senescence while extensive proliferation triggers replicative senescence also named as chronic senescence. In all conditions, but replicative and high IR dose senescence, we detected a reduction of the autophagic flux, while proteasome activity was impaired in peroxide-treated and irradiated cells. Differences were observed also in metabolic status. In general, all senescent cells evidenced metabolic inflexibility and prefer to use glucose as energy fuel. Irradiated cells with low dose of X-ray and replicative senescent cells show a residual capacity to use fatty acids and glutamine as alternative fuels, respectively. Our study may be useful to discriminate among different senescent phenotypes. PMID:26540573

The accumulation of cellular damage, including DNA damage, is thought to contribute to aging-related degenerative changes, but how damage drives aging is unknown. XFE progeroid syndrome is a disease of accelerated aging caused by a defect in DNA repair. NF-κB, a transcription factor activated by cellular damage and stress, has increased activity with aging and aging-related chronic diseases. To determine whether NF-κB drives aging in response to the accumulation of spontaneous, endogenous DNA damage, we measured the activation of NF-κB in WT and progeroid model mice. As both WT and progeroid mice aged, NF-κB was activated stochastically in a variety of cell types. Genetic depletion of one allele of the p65 subunit of NF-κB or treatment with a pharmacological inhibitor of the NF-κB-activating kinase, IKK, delayed the age-related symptoms and pathologies of progeroid mice. Additionally, inhibition of NF-κB reduced oxidative DNA damage and stress and delayed cellularsenescence. These results indicate that the mechanism by which DNA damage drives aging is due in part to NF-κB activation. IKK/NF-κB inhibitors are sufficient to attenuate this damage and could provide clinical benefit for degenerative changes associated with accelerated aging disorders and normal aging. PMID:22706308

A modest ethylene climacteric accompanies flower senescence in Mirabilis jalapa L., and exogenous ethylene accelerates the process. However, inhibitors of ethylene action and synthesis have little effect on the life-span of these ephemeral flowers. Treatment with '-amanitin, an inhibitor of DNA-de...

Purpose: MicroRNAs (miRNAs) have emerged as critical regulators of many cellular pathways. Ionizing radiation (IR) exposure causes DNA damage and induces premature senescence. However, the role of miRNAs in IR-induced senescence has not been well defined. Thus, the purpose of this study was to identify and characterize senescence-associated miRNAs (SA-miRNAs) and to investigate the role of SA-miRNAs in IR-induced senescence. Methods and Materials: In human lung (WI-38) fibroblasts, premature senescence was induced either by IR or busulfan (BU) treatment, and replicative senescence was accomplished by serial passaging. MiRNA microarray were used to identify SA-miRNAs, and real-time reverse transcription (RT)-PCR validated the expression profiles of SA-miRNAs in various senescent cells. The role of SA-miRNAs in IR-induced senescence was characterized by knockdown of miRNA expression, using anti-miRNA oligonucleotides or by miRNA overexpression through the transfection of pre-miRNA mimics. Results: We identified eight SA-miRNAs, four of which were up-regulated (miR-152, -410, -431, and -493) and four which were down-regulated (miR-155, -20a, -25, and -15a), that are differentially expressed in both prematurely senescent (induced by IR or BU) and replicatively senescent WI-38 cells. Validation of the expression of these SA-miRNAs indicated that down-regulation of miR-155, -20a, -25, and -15a is a characteristic miRNA expression signature of cellularsenescence. Functional analyses revealed that knockdown of miR-155 or miR-20a, but not miR-25 or miR-15a, markedly enhanced IR-induced senescence, whereas ectopic overexpression of miR-155 or miR-20a significantly inhibited senescence induction. Furthermore, our studies indicate that miR-155 modulates IR-induced senescence by acting downstream of the p53 and p38 mitogen-activated protein kinase (MAPK) pathways and in part via regulating tumor protein 53-induced nuclear protein 1 (TP53INP1) expression. Conclusion: Our

X-linked inhibitor of apoptosis (XIAP)-associated factor 1 (XAF1) is well known as an antagonist of XIAP-mediated caspase inhibition. Although XAF1 serves as a tumor-suppressor gene, the role of XAF1 in cellularsenescence remains unclear. We found that XAF1 expression was increased by genotoxic agents, such as doxorubicin and ionizing radiation in pulmonary microvascular endothelial cells, consequently leading to premature senescence. Conversely, downregulation of XAF1 in premature senescent cells partially overcame endothelial cell senescence. p53 knockdown, but not p16 knockdown, abolished senescence phenotypes caused by XAF1 induction. XAF1 expression was transcriptionally regulated by Bromodomain 7 (BRD7). XAF1 induction with interferon-gamma (IFN-γ) treatment was abrogated by BRD7 knockdown, which resulted in blocking interferon-induced senescence. In lung cancer cells, XAF1 tumor suppressor activity was decreased by BRD7 knockdown, and inhibition of tumor growth by IFN-γ did not appear in BRD7-depleted xenograft tumors. These data suggest that XAF1 is involved in BRD7-associated senescence and plays an important role in the regulation of endothelial senescence through a p53-dependent pathway. Furthermore, regulation of the BRD7/XAF1 system might contribute to tissue or organismal aging and protection against cellular transformation. PMID:26802028

X-linked inhibitor of apoptosis (XIAP)-associated factor 1 (XAF1) is well known as an antagonist of XIAP-mediated caspase inhibition. Although XAF1 serves as a tumor-suppressor gene, the role of XAF1 in cellularsenescence remains unclear. We found that XAF1 expression was increased by genotoxic agents, such as doxorubicin and ionizing radiation in pulmonary microvascular endothelial cells, consequently leading to premature senescence. Conversely, downregulation of XAF1 in premature senescent cells partially overcame endothelial cell senescence. p53 knockdown, but not p16 knockdown, abolished senescence phenotypes caused by XAF1 induction. XAF1 expression was transcriptionally regulated by Bromodomain 7 (BRD7). XAF1 induction with interferon-gamma (IFN-γ) treatment was abrogated by BRD7 knockdown, which resulted in blocking interferon-induced senescence. In lung cancer cells, XAF1 tumor suppressor activity was decreased by BRD7 knockdown, and inhibition of tumor growth by IFN-γ did not appear in BRD7-depleted xenograft tumors. These data suggest that XAF1 is involved in BRD7-associated senescence and plays an important role in the regulation of endothelial senescence through a p53-dependent pathway. Furthermore, regulation of the BRD7/XAF1 system might contribute to tissue or organismal aging and protection against cellular transformation. PMID:26802028

Cellularsenescence is a stable proliferation arrest that suppresses tumorigenesis. Cellularsenescence and associated tumor suppression depend on control of chromatin. Histone chaperone HIRA deposits variant histone H3.3 and histone H4 into chromatin in a DNA replication-independent manner. Appropriately for a DNA replication-independent chaperone, HIRA is involved in control of chromatin in nonproliferating senescent cells, although its role is poorly defined. Here, we show that nonproliferating senescent cells express and incorporate histone H3.3 and other canonical core histones into a dynamic chromatin landscape. Expression of canonical histones is linked to alternative mRNA splicing to eliminate signals that confer mRNA instability in nonproliferating cells. Deposition of newly synthesized histones H3.3 and H4 into chromatin of senescent cells depends on HIRA. HIRA and newly deposited H3.3 colocalize at promoters of expressed genes, partially redistributing between proliferating and senescent cells to parallel changes in expression. In senescent cells, but not proliferating cells, promoters of active genes are exceptionally enriched in H4K16ac, and HIRA is required for retention of H4K16ac. HIRA is also required for retention of H4K16ac in vivo and suppression of oncogene-induced neoplasia. These results show that HIRA controls a specialized, dynamic H4K16ac-decorated chromatin landscape in senescent cells and enforces tumor suppression. PMID:25512559

Cellularsenescence is a stable proliferation arrest that suppresses tumorigenesis. Cellularsenescence and associated tumor suppression depend on control of chromatin. Histone chaperone HIRA deposits variant histone H3.3 and histone H4 into chromatin in a DNA replication-independent manner. Appropriately for a DNA replication-independent chaperone, HIRA is involved in control of chromatin in nonproliferating senescent cells, although its role is poorly defined. Here, we show that nonproliferating senescent cells express and incorporate histone H3.3 and other canonical core histones into a dynamic chromatin landscape. Expression of canonical histones is linked to alternative mRNA splicing to eliminate signals that confer mRNA instability in nonproliferating cells. Deposition of newly synthesized histones H3.3 and H4 into chromatin of senescent cells depends on HIRA. HIRA and newly deposited H3.3 colocalize at promoters of expressed genes, partially redistributing between proliferating and senescent cells to parallel changes in expression. In senescent cells, but not proliferating cells, promoters of active genes are exceptionally enriched in H4K16ac, and HIRA is required for retention of H4K16ac. HIRA is also required for retention of H4K16ac in vivo and suppression of oncogene-induced neoplasia. These results show that HIRA controls a specialized, dynamic H4K16ac-decorated chromatin landscape in senescent cells and enforces tumor suppression. PMID:25512559

Heat stress-induced leaf senescence is characterized by the loss of chlorophyll from leaf tissues. The objectives of this study were to examine genetic variations in the level of heat-induced leaf senescence in hybrids of colonial (Agrostis capillaris)×creeping bentgrass (Agrostis stolonifera) contrasting in heat tolerance, and determine whether loss of leaf chlorophyll during heat-induced leaf senescence was due to suppressed chlorophyll synthesis and/or accelerated chlorophyll degradation in the cool-season perennial grass species. Plants of two hybrid backcross genotypes ('ColxCB169' and 'ColxCB190') were exposed to heat stress (38/33°C, day/night) for 28 d in growth chambers. The analysis of turf quality, membrane stability, photochemical efficiency, and chlorophyll content demonstrated significant variations in the level of leaf senescence induced by heat stress between the two genotypes, with ColXCB169 exhibiting a lesser degree of decline in chlorophyll content, photochemical efficiency and membrane stability than ColXCB190. The assays of enzymatic activity or gene expression of several major chlorophyll-synthesizing (porphobilinogen deaminase, Mg-chelatase, protochlorophyllide-reductase) and chlorophyll-degrading enzymes (chlorophyllase, pheophytinase, and chlorophyll-degrading peroxidase) indicated heat-induced decline in leaf chlorophyll content was mainly due to accelerated chlorophyll degradation, as manifested by increased gene expression levels of chlorophyllase and pheophytinase, and the activity of pheophytinase (PPH), while chlorophyll-synthesizing genes and enzymatic activities were not differentially altered by heat stress in the two genotypes. The analysis of heat-induced leaf senescence of pph mutants of Arabidopsis further confirmed that PPH could be one enzymes that plays key roles in regulating heat-accelerated chlorophyll degradation. Further research on enzymes responsible in part for the loss of chlorophyll during heat

The plastid-nucleus located protein WHIRLY1 has been described as an upstream regulator of leaf senescence, binding to the promoter of senescence-associated genes like HvS40. To investigate the impact of WHIRLY1 on drought stress-induced, premature senescence, transgenic barley plants with an RNAi-mediated knockdown of the HvWHIRLY1 gene were grown under normal and drought stress conditions. The course of leaf senescence in these lines was monitored by physiological parameters and studies on the expression of senescence- and drought stress-related genes. Drought treatment accelerated leaf senescence in WT plants, whereas WHIRLY 1 knockdown lines (RNAi-W1) showed a stay-green phenotype. Expression of both senescence-associated and drought stress-responsive genes, was delayed in the transgenic plants. Notably, expression of transcription factors of the WRKY and NAC families, which are known to function in senescence- and stress-related signaling pathways, was affected in plants with impaired accumulation of WHIRLY1, indicating that WHIRLY1 acts as an upstream regulator of drought stress-induced senescence. To reveal the epigenetic indexing of HvS40 at the onset of drought-induced senescence in WT and RNAi-W1 lines, stress-responsive loading with histone modifications of promoter and coding sequences of HvS40 was analyzed by chromatin immunoprecipitation and quantified by qRT-PCR. In the wildtype, the euchromatic mark H3K9ac of the HvS40 gene was low under control conditions and was established in response to drought treatment, indicating the action of epigenetic mechanisms in response to drought stress. However, drought stress caused no significant increase in H3K9ac in plants impaired in accumulation of WHIRLY1. The results show that WHIRLY1 knockdown sets in motion a delay in senescence that involves all aspects of gene expression, including changes in chromatin structure. PMID:27608048

Senescence--the progressive age-dependent decline in performance--occurs in most organisms. There is considerable variation in the onset and rate of senescence between and within species. Yet the causes of this variation are still poorly understood, despite being central to understanding the evolution of senescence. Long-term longitudinal studies on wild animals are extremely well-suited to studying the impact of environmental and individual characteristics (and the interaction between the two) on senescence, and can help us to understand the mechanisms that shape the evolution of senescence. In this review, we summarize and discuss the insights gained from our comprehensive long-term individual-based study of the Seychelles warbler (Acrocephalus sechellensis). This species provides an excellent model system in which to investigate the evolution of senescence in the wild. We found that Seychelles warblers show senescent declines in survival and reproduction, and discuss how individual characteristics (body condition, body size) and environmental effects (low- versus high-quality environments) may affect the onset and rate of senescence. Further, we highlight the evidence for trade-offs between early-life investment and senescence. We describe how key cellular and physiological processes (oxidative stress and telomere shortening) underpinning senescence are affected by individual and environmental characteristics in the Seychelles warbler (e.g. food availability, reproductive investment, disease) and we discuss how such physiological variation may mediate the relationship between environmental characteristics and senescence. Based on our work using Seychelles warblers as a model system, we show how insights from long-term studies of wild animals may help unravel the causes of the remarkable variation in senescence observed in natural systems, and highlight areas for promising future research. PMID:26344178

Cellularsenescence refers to irreversible growth arrest of primary eukaryotic cells, a process thought to contribute to aging-related degeneration and disease. Deficiency of RecQ helicase RECQL4 leads to Rothmund-Thomson syndrome (RTS), and we have investigated whether senescence is involved using cellular approaches and a mouse model. We first systematically investigated whether depletion of RECQL4 and the other four human RecQ helicases, BLM, WRN, RECQL1 and RECQL5, impacts the proliferative potential of human primary fibroblasts. BLM-, WRN- and RECQL4-depleted cells display increased staining of senescence-associated β-galactosidase (SA-β-gal), higher expression of p16(INK4a) or/and p21(WAF1) and accumulated persistent DNA damage foci. These features were less frequent in RECQL1- and RECQL5-depleted cells. We have mapped the region in RECQL4 that prevents cellularsenescence to its N-terminal region and helicase domain. We further investigated senescence features in an RTS mouse model, Recql4-deficient mice (Recql4(HD)). Tail fibroblasts from Recql4(HD) showed increased SA-β-gal staining and increased DNA damage foci. We also identified sparser tail hair and fewer blood cells in Recql4(HD) mice accompanied with increased senescence in tail hair follicles and in bone marrow cells. In conclusion, dysfunction of RECQL4 increases DNA damage and triggers premature senescence in both human and mouse cells, which may contribute to symptoms in RTS patients. PMID:24832598

Mutations in the tricarboxylic acid (TCA) cycle enzyme fumarate hydratase (FH) are associated with a highly malignant form of renal cancer. We combined analytical chemistry and metabolic computational modelling to investigate the metabolic implications of FH loss in immortalized and primary mouse kidney cells. Here, we show that the accumulation of fumarate caused by the inactivation of FH leads to oxidative stress that is mediated by the formation of succinicGSH, a covalent adduct between fumarate and glutathione. Chronic succination of GSH, caused by the loss of FH, or by exogenous fumarate, leads to persistent oxidative stress and cellularsenescence in vitro and in vivo. Importantly, the ablation of p21, a key mediator of senescence, in Fh1-deficient mice resulted in the transformation of benign renal cysts into a hyperplastic lesion, suggesting that fumarate-induced senescence needs to be bypassed for the initiation of renal cancers. PMID:25613188

Many genes and signaling pathways have been found to be involved in cellularsenescence program. In the present study, we have identified 16 senescence-associated genes by differential proteomic analysis of the normal human diploid fibroblast cell line, TIG-1, and focused on ATP6V0A2. The aim of this study is to clarify the role of ATP6V0A2, the causal gene for ARCL2, a syndrome of abnormal glycosylation and impaired Golgi trafficking, in cellularsenescence program. Here we showed that ATP6V0A2 is critical for cellularsenescence; impaired expression of ATP6V0A2 disperses the Golgi structure and triggers senescence, suggesting that ATP6V0A2 mediates these processes. FITC-lectin staining and glycoblotting revealed significantly different glycosylation structures in presenescent (young) and senescent (old) TIG-1 cells; reducing ATP6V0A2 expression in young TIG-1 cells yielded structures similar to those in old TIG-1 cells. Our results suggest that senescence-associated impaired expression of ATP6V0A2 triggers changes in Golgi structure and glycosylation in old TIG-1 cells, which demonstrates a role of ATP6V0A2 in cellularsenescence program. PMID:26611489

The nuclear receptor NR2E1 (also known as TLX or tailless) controls the self-renewal of neural stem cells (NSCs) and has been implied as an oncogene which initiates brain tumours including glioblastomas. Despite NR2E1 regulating targets like p21CIP1 or PTEN we still lack a full explanation for its role in NSC self-renewal and tumorigenesis. We know that Polycomb repressive complexes (PRC) also control stem cell self-renewal and tumorigenesis, but so far, no formal connection has been established between NR2E1 and PRCs. In a screen for transcription factors regulating the expression of the Polycomb protein CBX7, we identified NR2E1 as one of its more prominent regulators. NR2E1 binds at the CBX7 promoter, inducing its expression. Notably CBX7 represses NR2E1 as part of a regulatory loop. Ectopic NR2E1 expression inhibits cellularsenescence, extending cellular lifespan in fibroblasts via CBX7-mediated regulation of p16INK4a and direct repression of p21CIP1. In addition NR2E1 expression also counteracts oncogene-induced senescence (OIS). The importance of NR2E1 to restrain senescence is highlighted through the process of knocking down its expression, which causes premature senescence in human fibroblasts and epithelial cells. We also confirmed that NR2E1 regulates CBX7 and restrains senescence in NSCs. Finally, we observed that the expression of NR2E1 directly correlates with that of CBX7 in human glioblastoma multiforme. Overall we identified control of senescence and regulation of Polycomb action as two possible mechanisms that can join those so far invoked to explain the role of NR2E1 in control of NSC self-renewal and cancer. PMID:25328137

Investigations concerned with the effects of elevated atmospheric CO/sub 2/ on plant growth and senescence have generally involved short-term exposures. This report concerns the effects of lifetime exposures to elevated CO/sub 2/ levels in three native winter annual plant species on biomass accumulation, induction of flowering, leaf senescence, and death of whole plants. Life span was significantly (P < .05) reduced in Layia platyglossa and Clarkia rubicunda at the highest CO/sub 2/ concentrations (0.21%). Flower initiation was significantly (P < .05) accelerated for Layia platyglossa and Clarkia rubicunda at 0.14 and 0.21% CO. Dry matter accumulation (biomass) of Layia and Clarkia increased with increasing concentrations of atmospheric CO/sub 2/. The number of senesced leaves per plant during the early stages of development (pre-anthesis, 105 d) was not significantly different for CO/sub 2/ treatments for either Nemophila menziesii or Layia platyglossa.

The high prevalence of dementia in aged individuals suggests that aging is the most important risk factor and that senescence further enhances dementia. We have searched for dietary factors that prevent brain senescence using a mouse model of age-related neurodegeneration (SAMP10). This mouse line is suitable for studying brain senescence because brain atrophy and cognitive dysfunction are observed with aging, similar to humans. The production of reactive oxygen species and oxidative damage are high in the brains of aged SAMP10. We found that green tea catechin and β-cryptoxanthin in Japanese mandarin oranges prevented brain atrophy and cognitive dysfunction. In addition, psychosocially chronically stressed mice exhibited a shortened life span and accelerated cognitive dysfunction. These deficiencies were prevented by the ingestion of theanine, an amino acid in tea, under stressed conditions. While a number of factors affect brain senescence, our results suggest that non-nutritive food components such as catechin, β-cryptoxanthin and theanine may be useful for preventing brain senescence. PMID:25743897

Mesenchymal stem cells (MSCs) possess unique paracrine and immunosuppressive properties, which make them useful candidates for cellular therapy. Here, we address how cellularsenescence influences the therapeutic potential of human MSCs (hMSCs). Senescence was induced in bone marrow-derived hMSC cultures with gamma irradiation. Control and senescent cells were tested for their immunoregulatory activity in vitro and in vivo, and an extensive molecular characterization of the phenotypic changes induced by senescence was performed. We also compared the gene expression profiles of senescent hMSCs with a collection of hMSCs used in an ongoing clinical study of Graft Versus Host disease (GVHD). Our results show that senescence induces extensive phenotypic changes in hMSCs and abrogates their protective activity in a murine model of LPS-induced lethal endotoxemia. Although senescent hMSCs retain an ability to regulate the inflammatory response on macrophages in vitro, and, in part retain their capacity to significantly inhibit lymphocyte proliferation, they have a severely impaired migratory capacity in response to proinflammatory signals, which is associated with an inhibition of the AP-1 pathway. Additionally, expression analysis identified PLEC, C8orf48, TRPC4, and ZNF14, as differentially regulated genes in senescent hMSCs that were similarly regulated in those hMSCs which failed to produce a therapeutic effect in a GVHD trial. All the observed phenotypic alterations were confirmed in replicative-senescent hMSCs. In conclusion, this study highlights important changes in the immunomodulatory phenotype of senescent hMSCs and provides candidate gene signatures which may be useful to evaluate the therapeutic potential of hMSCs used in future clinical studies. PMID:24496748

TAp73, a member of the p53 family, has been traditionally considered a tumor suppressor gene, but a recent report has claimed that it can promote cellular proliferation. This assumption is based on biochemical evidence of activation of anabolic metabolism, with enhanced pentose phosphate shunt (PPP) and nucleotide biosynthesis. Here, while we confirm that TAp73 expression enhances anabolism, we also substantiate its role in inhibiting proliferation and promoting cell death. Hence, we would like to propose an alternative interpretation of the accumulating data linking p73 to cellular metabolism: we suggest that TAp73 promotes anabolism to counteract cellularsenescence rather than to support proliferation. PMID:25554796

Impaired glucose tolerance characterized by postprandial hyperglycemia, which occurs frequently in elderly persons and represents an important preliminary step in diabetes mellitus, poses an independent risk factor for the development of atherosclerosis. Endothelial cellularsenescence is reported to precede atherosclerosis. We reported that continuous high glucose stimulus causes endothelial senescence more markedly than hypertension or dyslipidemia stimulus. In the present study, we evaluated the effect of fluctuating glucose levels on human endothelial senescence. Constant high glucose increased senescence-associated-β-galactosidase(SA-β-gal) activity, a widely used marker for cellularsenescence. Interestingly, in intermittent high glucose, this effect was more pronounced as well as increase of p21 and p16INK4a , senescence related proteins with DNA damage. However, telomerase was not activated and telomere length was not shortened, thus stress-induced senescence was shown. However, constant high glucose activated telomerase and shortened telomere length, which suggested replicative senescence. Intermittent but not constant high glucose strikingly up-regulated the expression of p22phox, an NADPH oxidase component, increasing superoxide. The small interfering RNA of p22phox undermined the increase in SA-β-gal activity induced by intermittent high glucose. Conclusively, intermittent high glucose can promote vascular endothelial senescence more than constant high glucose, which is in partially dependent on superoxide overproduction. PMID:25879533

Werner's syndrome (WS) is an autosomal recessive genetic disorder caused by loss of function mutation in wrn and is a useful model of premature in vivo ageing. Cellularsenescence is a plausible causal mechanism of mammalian ageing and, at the cellular level, WS fibroblasts show premature senescence resulting from a combination of telomeric attrition and replication fork stalling. Over 90% of WS fibroblast cultures achieve <20 population doublings (PD) in vitro compared to wild type human fibroblast cultures. It has been proposed that some cell types, capable of proliferation, will fail to show a premature senescence phenotype in response to wrn mutations. To test this hypothesis, human dermal keratinocytes (derived from both WS and wild type patients) were cultured long term. WS Keratinocytes showed a replicative lifespan in excess of 100 population doublings but maintained functional growth arrest mechanisms based on p16 and p53. The karyotype of the cells was superficially normal and the cultures retained markers characteristic of keratinocyte holoclones (stem cells) including p63 expression and telomerase activity. Accordingly we conclude that, in contrast to WS fibroblasts, WS keratinocytes do not demonstrate slow growth rates or features of premature senescence. These findings suggest that the epidermis is among the tissue types that do not display symptoms of premature ageing caused by loss of function of wrn. This is in support that Werner's syndrome is a segmental progeroid syndrome. PMID:27492502

Age is a risk factor for cardiovascular disease, suggesting a causal relationship between age-related changes and vascular damage. Endothelial dysfunction is an early pathophysiological hallmark in the development of cardiovascular disease. Senescence, the cellular equivalent of aging, was proposed to be involved in endothelial dysfunction, but functional data showing a causal relationship are missing.Endothelium-dependent vasodilation was measured in aortic rings ex vivo. We investigated aortas from aged C57Bl/6 mice (24-28 months), in which p16 (INK4a) and p19 (ARF) expression, markers of stress-induced senescence, were significantly induced compared to young controls (4-6 months). To reflect telomere shortening in human aging, we investigated aortas from telomerase deficient (Terc(-/-)) mice of generation 3 (G3). Endothelium-dependent vasodilation in aged wildtype and in Terc(-/-) G3 mice was impaired. A combination of the superoxide dismutase mimetic 1-Oxyl-2,2,6, 6-tetramethyl-4-hydroxypiperidine (TEMPOL) and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin significantly improved endothelium-dependent vasodilation in aged wildtype and Terc(-/-) G3 mice compared to untreated controls. We show that both, aging and senescence induced by telomere shortening, cause endothelial dysfunction that can be restored by antioxidants, indicating a role for oxidative stress. The observation that cellularsenescence is a direct signalling event leading to endothelial dysfunction holds the potential to develop new targets for the prevention of cardiovascular disease. PMID:25735595

Ionizing radiation induces cellularsenescence to suppress cancer cell proliferation. However, it also induces deleterious bystander effects in the unirradiated neighboring cells through the release of senescence-associated secretory phenotypes (SASPs) that promote tumor progression. Although autophagy has been reported to promote senescence, its role is still unclear. We previously showed that radiation induces senescence in PTTG1-depleted cancer cells. In this study, we found that autophagy was required for the radiation-induced senescence in PTTG1-depleted breast cancer cells. Inhibition of autophagy caused the cells to switch from radiation-induced senescence to apoptosis. Senescent cancer cells exerted bystander effects by promoting the invasion and migration of unirradiated cells through the release of CSF2 and the subsequently activation of the JAK2-STAT3 and AKT pathways. However, the radiation-induced bystander effects were correlated with the inhibition of endogenous autophagy in bystander cells, which also resulted from the activation of the CSF2-JAK2 pathway. The induction of autophagy by rapamycin reduced the radiation-induced bystander effects. This study reveals, for the first time, the dual role of autophagy in radiation-induced senescence and bystander effects. PMID:24813621

Cellularsenescence is a stable cell cycle arrest that limits the proliferation of pre-cancerous cells. Here we demonstrate that scaffold-attachment-factor A (SAFA) and the long noncoding RNA PANDA differentially interact with polycomb repressive complexes (PRC1 and PRC2) and the transcription factor NF-YA to either promote or suppress senescence. In proliferating cells, SAFA and PANDA recruit PRC complexes to repress the transcription of senescence-promoting genes. Conversely, the loss of SAFA–PANDA–PRC interactions allows expression of the senescence programme. Accordingly, we find that depleting either SAFA or PANDA in proliferating cells induces senescence. However, in senescent cells where PANDA sequesters transcription factor NF-YA and limits the expression of NF-YA-E2F-coregulated proliferation-promoting genes, PANDA depletion leads to an exit from senescence. Together, our results demonstrate that PANDA confines cells to their existing proliferative state and that modulating its level of expression can cause entry or exit from senescence. PMID:25406515

Cellularsenescence is an irreversible block of cellular division, and induction of senescence is being considered for treatment of many cancer types, mainly those resistant to classical pro-apoptotic therapies. Resveratrol (Rsv) and quercetin (Quer), two natural polyphenols, are able to induce senescence in different cancer models, including gliomas, the most common and aggressive primary brain tumor. These polyphenols modulate the activity of several proteins involved in cell growth and death in cancer cells, including histone deacetylases (HDAC), but the role of HDAC in senescence induced by Rsv and Quer is unclear. The HDAC inhibitor sodium butyrate (NaB) potentiated the pro-senescent effect of Rsv and Quer in human and rat glioma cell lines but not in normal rat astrocytes. Furthermore, the increment of Quer-induced senescence by NaB was accompanied by an increase of reactive oxygen species levels and an increment of the number of cells with nuclear abnormalities. Altogether, these data support a positive role of HDAC inhibition on the senescence induced by these polyphenols, and therefore co-treatment of HDAC inhibitors and polyphenols emerges as a potential alternative for gliomas. PMID:25070040

Plant senescence is largely influenced by carbohydrate content. In order to investigate the impact of carbohydrate content on leaf senescence and photosystem II (PSII) during the senescence process, phloem girdling (PG), leaf removal (LR) and a combination of phloem girdling and leaf removal (GR) were performed on Alhagi sparsifolia (Fabaceae) at the end of the growing season. The results showed that during senescence, leaf soluble sugar content, starch content, the energy absorbed by the unit reaction centre (ABS/RC) increased; whereas, leaf photosynthetic rate, photosynthetic pigment content, maximum photochemical efficiency (φPo ) and energy used by the acceptor site in electron transfer (ETo/RC) decreased. The degree of change was PG > GR > CK (control) > LR. The results of the present work implied that phloem girdling (PG) significantly accelerated leaf senescence, and that single leaf removal (LR) slightly delayed leaf senescence; although leaf removal significantly delayed the senescence process on the girdled leaf (GR). Natural or delayed senescence only slightly inhibited the acceptor site of PSII and did not damage the donor site of PSII. On the other hand, induced senescence not only damaged the donor site of PSII (e.g. oxygen-evolving complex), but also significantly inhibited the acceptor site of PSII. In addition, leaf senescence led to an increase in the energy absorbed by the unit reaction centre (ABS/RC), which subsequently resulted in increasing excitation pressure in the reaction centre (DIo/RC), as well as additional saved Car for absorbing residual light energy and quenching reactive oxygen species during senescence. PMID:25662611

There is growing evidence that senescent cells accumulate in vivo and are associated with the aging process in parallel with the progressive erosion of telomeres. Because recent data show that telomere shortening is involved in the pathogenesis of liver cirrhosis, we looked for replicative senescence cells in normal livers, chronic hepatitis C, and hepatocellular carcinoma (HCC). Replicative senescent cells were detected on liver tissue cryosections using expression of a specific marker, senescence-associated beta-galactosidase, a cytoplasmic enzyme detected at pH 6. A total of 57 frozen liver samples (15 normal liver, 32 chronic hepatitis C, and 10 HCCs) were studied. Replicative senescence was graded as absent in 56% of cases (32 of 57) and present in 44% (25 of 57). Replicative senescence was considered present in 3 of 15 normal livers (20%), 16 of 32 chronic hepatitis cases (50%), and 6 of 10 HCCs (60%). In the group of nontumoral livers, the presence of senescent cells in liver was associated with older age (P =.03). In the group with chronic hepatitis C, fibrosis stage, but not activity grade, was significantly correlated with the accumulation of replicative senescent cells (P accelerated replicative senescence and that accumulation of replicative senescent cells predispose to HCC development. Detection of replicative senescent cells may then serve as a predictive marker of a hepatocellular carcinoma in the surrounding tissue. HUM PATHOL 32:327-332. PMID:11274643

The rate of senescence can be inferred from the acceleration by which mortality rates increase over age. Such a senescence rate is generally estimated from parameters of a mathematical model fitted to these mortality rates. However, such models have limitations and underlying assumptions. Notably, they do not fit mortality rates at young and old ages. Therefore, we developed a method to calculate senescence rates from the acceleration of mortality directly without modeling the mortality rates. We applied the different methods to age group-specific mortality data from the European Renal Association-European Dialysis and Transplant Association Registry, including patients with end-stage renal disease on dialysis, who are known to suffer from increased senescence rates (n = 302,455), and patients with a functioning kidney transplant (n = 74,490). From age 20 to 70, senescence rates were comparable when calculated with or without a model. However, when using non-modeled mortality rates, senescence rates were yielded at young and old ages that remained concealed when using modeled mortality rates. At young ages senescence rates were negative, while senescence rates declined at old ages. In conclusion, the rate of senescence can be calculated directly from non-modeled mortality rates, overcoming the disadvantages of an indirect estimation based on modeled mortality rates. PMID:25887122

Several lines of mouse mammary tissue that had been serially transplanted until mitotic senescence was reached were exposed in vivo to plastic implants that slowly released cholera toxin. Gland tissue surrounding the implants displayed new end buds, indicating reinitiation of growth and morphogenesis. The ability of cholera toxin, which elevates intracellular adenosine 3',5'-monophosphate, to temporarily reverse the senescent phenotype suggests that this mitotic dysfunction results not from generalized cellular deterioration but from specific changes in cell regulation.

In addition to floral senescence and longevity, the control of leaf senescence is a major factor determining the quality of several cut flowers, including Lilium, in the commercial market. To better understand the physiological process underlying leaf senescence in this species, we evaluated: (i) endogenous variation in the levels of phytohormones during leaf senescence, (ii) the effects of leaf darkening in senescence and associated changes in phytohormones, and (iii) the effects of spray applications of abscisic acid (ABA) and pyrabactin on leaf senescence. Results showed that while gibberellin 4 (GA(4)) and salicylic acid (SA) contents decreased, that of ABA increased during the progression of leaf senescence. However, dark-induced senescence increased ABA levels, but did not affect GA(4) and SA levels, which appeared to correlate more with changes in air temperature and/or photoperiod than with the induction of leaf senescence. Furthermore, spray applications of pyrabactin delayed the progression of leaf senescence in cut flowers. Thus, we conclude that (i) ABA plays a major role in the regulation of leaf senescence in Lilium, (ii) darkness promotes leaf senescence and increases ABA levels, and (iii) exogenous applications of pyrabactin inhibit leaf senescence in Lilium, therefore suggesting that it acts as an antagonist of ABA in senescing leaves of cut lily flowers. PMID:22854182

In recent years, the artificial cultivation of Morchella mushrooms that belong to Elata Clade, including Morchella elata, has been developed rapidly in China. However, the prominent problem of spawn aging has been frustrating the morel farming. In this paper, aging in M. elata was achieved from 12 to 17 subcultures and lifespan of 1536-2256 h by successive subculturing. The lifespan can be roughly divided into juvenile phase and senescent phase with respect to the mycelia linear growth rate. After a certain period of rapid growth with almost constant rate at the juvenile phase, the isolate entered the senescent phase characterized by slow down of mycelia growth, producing pigments ahead of time and final death of the apical hyphae. The period of the senescent phase was definitely 240-288 h; while that of the juvenile phase was diverse relying on different isolates. Moreover, microscopic study showed that angles between the leading and primary hyphae increased constantly with aging. In senesced hyphal cells of M. elata, the typical characteristics of autophagy (enlargement of vacuoles and existence of organelles sequestrated lysosomes) and apoptosis (condensation of the cytoplasm and nuclear and plasmolysis) were observed. In addition, in the final stage of senescence, the apical hyphae collapsed with the plasma membrane and all the cellular organelles disrupted, indicated a necrotic mode of cell death. Taken together, these data revealed the involvement of autophagy, apoptosis and necrosis in senescence of M. elata. The characterization and molecular mechanism of autophagy, apoptosis and necrosis need further study and the systematic study of morel aging will be beneficial for the healthy development of morel farming. PMID:26281756

Despite recent insights into prostate cancer (PCa)-associated genetic changes, full understanding of prostate tumorigenesis remains elusive owing to complexity of interactions among various cell types and soluble factors present in prostate tissue. We found the upregulation of nuclear factor of activated T cells c1 (NFATc1) in human PCa and cultured PCa cells, but not in normal prostates and non-tumorigenic prostate cells. To understand the role of NFATc1 in prostate tumorigenesis in situ, we temporally and spatially controlled the activation of NFATc1 in mouse prostate and showed that such activation resulted in prostatic adenocarcinoma with features similar to those seen in human PCa. Our results indicate that the activation of a single transcription factor, NFATc1 in prostatic luminal epithelium to PCa can affect expression of diverse factors in both cells harboring the genetic changes and in neighboring cells through microenvironmental alterations. In addition to the activation of oncogenes c-MYC and STAT3 in tumor cells, a number of cytokines and growth factors, such as IL1β, IL6 and SPP1 (osteopontin, a key biomarker for PCa), were upregulated in NFATc1-induced PCa, establishing a tumorigenic microenvironment involving both NFATc1 positive and negative cells for prostate tumorigenesis. To further characterize interactions between genes involved in prostate tumorigenesis, we generated mice with both NFATc1 activation and Pten inactivation in prostate. We showed that NFATc1 activation led to acceleration of Pten null-driven prostate tumorigenesis by overcoming the PTEN loss-induced cellularsenescence through inhibition of p21 activation. This study provides direct in vivo evidence of an oncogenic role of NFATc1 in prostate tumorigenesis and reveals multiple functions of NFATc1 in activating oncogenes, in inducing proinflammatory cytokines, in oncogene addiction, and in overcoming cellularsenescence, which suggests calcineurin-NFAT signaling as a potential

Generation of reactive oxygen species (ROS) is one of the earliest responses of plant cells to various biotic and abiotic stresses. ROS are capable of inducing cellular damage by oxidation of proteins, inactivation of enzymes, alterations in the gene expression, and decomposition of biomembranes. On the other hand, they also have a signaling role and changes in production of ROS can act as signals that change the transcription of genes that favor the acclimation of plants to abiotic stresses. Among the ROS, it is believed that H2O2 causes the largest changes in the levels of gene expression in plants. A wide range of plant responses has been found to be triggered by H2O2 such as acclimation to drought, photooxidative stress, and induction of senescence. Our knowledge on signaling roles of singlet oxygen (1O2) has been limited by its short lifetime, but recent experiments with a flu mutant demonstrated that singlet oxygen does not act primarily as a toxin but rather as a signal that activates several stress-response pathways. In this review we summarize the latest progress on the signaling roles of ROS during senescence and abiotic stresses and we give a short overview of the methods that can be used for their assessment. PMID:27135335

In the last decades, cellularsenescence is viewed as a complex mechanism involved in different processes, ranging from tumor suppression to induction of age-related degenerative alterations. Senescence-inducing stimuli are myriad and, recently, we and others have demonstrated the role exerted by microRNAs in the induction and maintenance of senescence, by the identification of a subset of Senescence-Associated microRNAs (SAmiRs) up-regulated during replicative or stress-induced senescence and able to induce a premature senescent phenotype when over-expressed in human primary cells. With the intent to find novel direct targets of two specific SAmiRs, SAmiR-494 and -486-5p, and cellular pathways which they are involved in, we performed a comparative analysis of gene expression profiles available in literature to select genes down-regulated upon replicative senescence of human primary fibroblasts. Among them, we searched for SAmiR’s candidate targets by analyzing with different target prediction algorithms their 3’UTR for the presence of SAmiR-binding sites. The expression profiles of selected candidates have been validated on replicative and stress-induced senescence and the targeting of the 3’UTRs was assessed by luciferase assay. Results allowed us to identify Cell Division Cycle Associated 2 (CDCA2) and Inhibitor of DNA binding/differentiation type 4 (ID4) as novel targets of SAmiR-494 and SAmiR-486-5p, respectively. Furthermore, we demonstrated that the over-expression of CDCA2 in human primary fibroblasts was able to partially counteract etoposide-induced senescence by mitigating the activation of DNA Damage Response. PMID:24905922

Stress induced premature senescence (SIPS) is a relative extension to the concept of exogenous cellular insult. Besides persistent double strand (ds) DNA breaks and increased β-galactosidase activity, biological significance of telomeric attrition in conjunction with senescence associated secretory phenotype (SASP) has been highlighted in SIPS. To gain insight on the potential role of this unique phenomenon invoked upon environmental stress, we sequentially validated the molecular repercussions of this event in ovarian epithelial cells after exposure to methyl isocyanate, an elegant regulator of cellular biotransformation. Persistent accumulation of DNA damage response factors phospho-ATM/γ-H2AX, morphological changes with increased cell size and early yet incremental β-gal staining, imply the inception of premature senescence. Advent of SASP is attributed by prolonged secretion of pro-inflammatory cytokines along with untimely but significant G1/S cell cycle arrest. Telomeric dysfunction associated with premature senescence is indicative of early loss of TRF2 (telomeric repeat binding factor 2) protein and resultant multiple translocations. Induction of senescence-associated heterochromatic foci formation showcases the chromatin alterations in form of trimethylated H3K9me3 in conjunction with H4 hypoacetylation and altered miRNA expression. Anchorage-independent neoplastic growth observed in treated cells reaffirms the oncogenic transformation following the exposure. Collectively, we infer the possible role of SIPS, as a central phenomenon, to perturbed genomic integrity in ovarian surface epithelium, orchestrated through SASP and chromatin level alterations, a hitherto unknown molecular paradigm. Although translational utility of SIPS as a biomarker for estimating ovarian cancer risk seems evident, further investigations will be imperative to provide a tangible way for its precise validation in clinical settings. PMID:25673532

Objective Cellularsenescence influences organismal aging and increases predisposition to age-related diseases, in particular cardiovascular disease, a leading cause of death and disability worldwide. PGC-1α is a master regulator of mitochondrial biogenesis and function, oxidative stress and insulin resistance. Senescence is associated with telomere and mitochondrial dysfunction and oxidative stress, inferring a potential causal role of PGC-1α in senescence pathogenesis. Methods and Results We generated a PGC-1α+/−/ApoE−/− mouse model and show that PGC-1α deficiency promotes a vascular senescence phenotype that is associated with increased oxidative stress, mitochondrial abnormalities, and reduced telomerase activity. PGC-1α disruption results in reduced expression of the longevity-related deacetylase sirtuin 1 (SIRT1) and the antioxidant catalase, and increased expression of the senescence marker p53 in aortas. Further, angiotensin II (Ang II), a major hormonal inducer of vascular senescence, induces prolonged lysine acetylation of PGC-1α and releases the PGC-1α·FoxO1 complex from the SIRT1 promoter, thus reducing SIRT1 expression. The phosphorylation defective mutant PGC-1α S570A is not acetylated, is constitutively active for FoxO1-dependent SIRT1 transcription and prevents Ang II-induced senescence. Acetylation of PGC-1α by Ang II interrupts the PGC-1α-FoxO1-SIRT1 feed-forward signaling circuit leading to SIRT1 and catalase downregulation and vascular senescence. Conclusions PGC-1α is a primary negative regulator of vascular senescence. Moreover, the central role of post-translational modification of PGC-1α in regulating Ang II-induced vascular senescence may inform development of novel therapeutic strategies for mitigating age-associated diseases such as atherosclerosis. PMID:23430617

1. Senescence, the physiological decline that results in decreasing survival and/or reproduction with age, remains one of the most perplexing topics in biology. Most theories explaining the evolution of senescence (i.e. antagonistic pleiotropy, accumulation of mutations, disposable soma) were developed decades ago. Even though these theories have implicitly focused on unitary animals, they have also been used as the foundation from which the universality of senescence across the tree of life is assumed. 2. Surprisingly, little is known about the general patterns, causes and consequences of whole-individual senescence in the plant kingdom. There are important differences between plants and most animals, including modular architecture, the absence of early determination of cell lines between the soma and gametes, and